Squashed commit of the following:

include/nuttx/arch.h:  Add prototype for an architecture-specific up_trigger_irq function
    arch/, include/nuttx, sched/sched:  Add the garbage collection hook so each architecture can do custom memory cleanup if necesary.
    arch/Kconfig:  Add configureation CONFIG_ARCH_GNU_NO_WEAKFUNCTIONS to suppress use of weak functions.  Some gnu derived toolchains do not support weak symbols

arch/Kconfig

@@ -139,6 +139,13 @@ config ARCH_TOOLCHAIN_GNU
 	bool
 	default n
 
+config ARCH_GNU_NO_WEAKFUNCTIONS
+	bool
+	depends on ARCH_TOOLCHAIN_GNU
+	default n
+	---help---
+		Disable support for weak functions.
+
 comment "Architecture Options"
 
 config ARCH_NOINTC
@@ -222,6 +229,10 @@ config ARCH_HAVE_RTC_SUBSECONDS
 	bool
 	default n
 
+config ARCH_HAVE_GARBAGE
+	bool
+	default n
+
 config ARCH_GLOBAL_IRQDISABLE
 	bool
 	default n