!compiler: drop CONFIG_HAVE_LONG_LONG and require long long support

Every compiler supported by NuttX provides the "long long" types,
so the CONFIG_HAVE_LONG_LONG indirection is no longer useful.
Remove the option from include/nuttx/compiler.h and treat
"long long" as unconditionally available across the OS.

In addition to deleting the guard itself, this commit unconditionally
enables the long-long flavored helpers that used to be gated behind
it:

  - libs/libc/fixedmath: drop the soft-emulated b32/ub32 routines
    in lib_fixedmath.c (-261 lines) and trim the matching
    prototypes, Make.defs and CMakeLists.txt entries; keep only
    the long-long backed implementations.
  - include/sys/endian.h, include/strings.h, libs/libc/string
    /lib_ffsll.c, lib_flsll.c: always expose the 64-bit byte-swap
    and ffsll/flsll variants.
  - libs/libm/libm/lib_llround{,f,l}.c: drop the empty stubs.
  - libs/libc/stdlib (atoll, llabs, lldiv, strtoll/ull, rand48,
    strtold), libs/libc/stream (libvsprintf, libvscanf,
    libbsprintf, ultoa_invert), libs/libc/misc (crc64, crc64emac),
    libs/libc/inttypes/strtoimax, libs/libc/lzf, libs/libc/libc.csv,
    libs/libc/string (memset, vikmemcpy): remove the
    #ifdef CONFIG_HAVE_LONG_LONG branches.
  - include/{stddef.h,stdlib.h,fixedmath.h,sys/epoll.h,cxx/cstdlib,
    nuttx/audio/audio.h,nuttx/crc64.h,nuttx/lib/math.h,
    nuttx/lib/math32.h,nuttx/lib/stdbit.h}: same guard cleanup.
  - drivers/note/note_driver.c, fs/spiffs/src/spiffs.h,
    sched/irq/irq_procfs.c: drop their local guards as well.
  - Documentation/applications/netutils/ntpclient/index.rst:
    refresh the documentation snippet.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

include/sys/endian.h

@@ -71,20 +71,18 @@
                ((((uint32_t)(n)) & 0xff000000UL) >> 24))
 #endif
 
-#ifdef CONFIG_HAVE_LONG_LONG
-#  ifdef CONFIG_HAVE_BUILTIN_BSWAP64
-#    define __swap_uint64(n) ((uint64_t)__builtin_bswap64(n))
-#  else
-#    define __swap_uint64(n) \
-        (uint64_t)(((((uint64_t)(n)) & 0x00000000000000ffULL) << 56) | \
-                   ((((uint64_t)(n)) & 0x000000000000ff00ULL) << 40) | \
-                   ((((uint64_t)(n)) & 0x0000000000ff0000ULL) << 24) | \
-                   ((((uint64_t)(n)) & 0x00000000ff000000ULL) <<  8) | \
-                   ((((uint64_t)(n)) & 0x000000ff00000000ULL) >>  8) | \
-                   ((((uint64_t)(n)) & 0x0000ff0000000000ULL) >> 24) | \
-                   ((((uint64_t)(n)) & 0x00ff000000000000ULL) >> 40) | \
-                   ((((uint64_t)(n)) & 0xff00000000000000ULL) >> 56))
-#  endif
+#ifdef CONFIG_HAVE_BUILTIN_BSWAP64
+#  define __swap_uint64(n) ((uint64_t)__builtin_bswap64(n))
+#else
+#  define __swap_uint64(n) \
+      (uint64_t)(((((uint64_t)(n)) & 0x00000000000000ffULL) << 56) | \
+                 ((((uint64_t)(n)) & 0x000000000000ff00ULL) << 40) | \
+                 ((((uint64_t)(n)) & 0x0000000000ff0000ULL) << 24) | \
+                 ((((uint64_t)(n)) & 0x00000000ff000000ULL) <<  8) | \
+                 ((((uint64_t)(n)) & 0x000000ff00000000ULL) >>  8) | \
+                 ((((uint64_t)(n)) & 0x0000ff0000000000ULL) >> 24) | \
+                 ((((uint64_t)(n)) & 0x00ff000000000000ULL) >> 40) | \
+                 ((((uint64_t)(n)) & 0xff00000000000000ULL) >> 56))
 #endif
 
 /* Endian-specific definitions */
@@ -107,12 +105,10 @@
 #  define be32toh(n)          ((uint32_t)(n))
 #  define le32toh(n)          __swap_uint32(n)
 
-#  ifdef CONFIG_HAVE_LONG_LONG
-#    define htobe64(n)        ((uint64_t)(n))
-#    define htole64(n)        __swap_uint64(n)
-#    define be64toh(n)        ((uint64_t)(n))
-#    define le64toh(n)        __swap_uint64(n)
-#  endif
+#  define htobe64(n)          ((uint64_t)(n))
+#  define htole64(n)          __swap_uint64(n)
+#  define be64toh(n)          ((uint64_t)(n))
+#  define le64toh(n)          __swap_uint64(n)
 
 #else
 /* Little-endian byte order */
@@ -132,12 +128,10 @@
 #  define be32toh(n)          __swap_uint32(n)
 #  define le32toh(n)          ((uint32_t)(n))
 
-#  ifdef CONFIG_HAVE_LONG_LONG
-#    define htobe64(n)        __swap_uint64(n)
-#    define htole64(n)        ((uint64_t)(n))
-#    define be64toh(n)        __swap_uint64(n)
-#    define le64toh(n)        ((uint64_t)(n))
-#  endif
+#  define htobe64(n)          __swap_uint64(n)
+#  define htole64(n)          ((uint64_t)(n))
+#  define be64toh(n)          __swap_uint64(n)
+#  define le64toh(n)          ((uint64_t)(n))
 #endif
 
 /* OpenBSD style */
@@ -159,13 +153,11 @@
 #define lemtoh32(x)           letoh32(*(FAR uint32_t *)(x))
 #define htolem32(x, v)        (*(FAR uint32_t *)(x) = htole32(v))
 
-#ifdef CONFIG_HAVE_LONG_LONG
-#  define betoh64             be64toh
-#  define letoh64             le64toh
-#  define bemtoh64(x)         betoh64(*(FAR uint64_t *)(x))
-#  define htobem64(x, v)      (*(FAR uint64_t *)(x) = htobe64(v))
-#  define lemtoh64(x)         letoh64(*(FAR uint64_t *)(x))
-#  define htolem64(x, v)      (*(FAR uint64_t *)(x) = htole64(v))
-#endif
+#define betoh64               be64toh
+#define letoh64               le64toh
+#define bemtoh64(x)           betoh64(*(FAR uint64_t *)(x))
+#define htobem64(x, v)        (*(FAR uint64_t *)(x) = htobe64(v))
+#define lemtoh64(x)           letoh64(*(FAR uint64_t *)(x))
+#define htolem64(x, v)        (*(FAR uint64_t *)(x) = htole64(v))
 
 #endif /* __INCLUDE_SYS_ENDIAN_H */

include/sys/epoll.h

@@ -102,9 +102,7 @@ union epoll_data
   FAR void    *ptr;
   int          fd;
   uint32_t     u32;
-#ifdef CONFIG_HAVE_LONG_LONG
   uint64_t     u64;
-#endif
 };
 
 typedef union epoll_data epoll_data_t;