[merge] branch 'heapswitch'

This picks up the major work of allowing multiple heap implementations
and enable dlmalloc as an alternate heap to the simple existing one
(now called 'miniheap').

Also added a novm page allocator for memory management on systems too small
or missing an mmu to have a vm. Not much more than a simple bitmap allocator
that the heap pulls from. Allows for other heaps and/or users of physical
memory to coexist and span multiple banks of memory.

platform/armemu/rules.mk

@@ -29,10 +29,6 @@ MODULE_DEPS += \
 MEMBASE := 0x0
 MEMSIZE := 0x400000	# 4MB
 
-GLOBAL_DEFINES += \
-	MEMBASE=$(MEMBASE) \
-	MEMSIZE=$(MEMSIZE)
-
 LINKER_SCRIPT += \
 	$(BUILDDIR)/system-onesegment.ld