Merged in paimonen/nuttx/pullreq_libc_libnx_updates (pull request #757)

Pullreq libc libnx updates

* NuttX: make strerror() return 'Success' for 0

* NuttX: fix strrchr() so that it considers null terminator as part of string

    From strrchr(3) man page:
    "The terminating null byte is considered part of the string, so that if c
    is specified as '\0', these functions return a pointer to the terminator."

* NuttX: mm_free(): Add DEBUGASSERT()'s to catch memory corruption early.

    It's easier to find the source when asserts fail already when freeing
    an overflowed buffer, than if the corruption is only detected on next
    malloc().

* MM_FILL_ALLOCATIONS: Add debug option to fill all mallocs()

    This is helpful for detecting uninitialized variables,
    especially in C++ code. I seem to be forgetting to initialize
    member variables and then they just get random values..

* NuttX: nxtk_bitmapwindow: Fix warning message when bitmap is fully off-screen.

* nxfonts_getfont: Avoid unnecessary warnings for other whitespace chars also.

* NuttX: Fix kerning of 'I' in Sans17x22 font

    The I character was running together with some other
    characters, e.g. in sequence "IMI".

* NXMU: Revalidate window pointer for mouse events.

    NXMU caches the previous window pointer so that further mouse
    events can be sent to the same window. However, if the window
    is destroyed while mouse button is held down, the pointer may
    become invalid and cause a crash. This patch revalidates the
    pointer before using it.

Approved-by: GregoryN <gnutt@nuttx.org>

mm/Kconfig

@@ -148,4 +148,11 @@ config MM_SHM
 		Build in support for the shared memory interfaces shmget(), shmat(),
 		shmctl(), and shmdt().
 
+config MM_FILL_ALLOCATIONS
+	bool "Fill allocations with debug value"
+	default n
+	---help---
+		Fill all malloc() allocations with 0xAA. This helps
+		detecting uninitialized variable errors.
+
 source "mm/iob/Kconfig"