* lib/jit_memory.c: Implement a simple memory allocation wrapper
to allow overriding calls to malloc/calloc/realloc/free, as well
as ensuring all memory containing pointers is zero or points to
allocated memory.
* include/lightning.h, include/lightning/jit_private.h: Definitions
for the memory allocation wrapper.
* lib/Makefile.am: Update for new jit_memory.c file.
* lib/jit_arm.c, lib/jit_disasm.c, lib/jit_mips.c, lib/jit_note.c,
lib/jit_ppc.c, lib/jit_sparc.c, lib/jit_x86.c, lib/lightning.c:
Use the new memory allocation wrapper code.
