libualloc examples

• Makefile to compile a_ and b_ examples
• Examples on using the different (high level) allocators (lib link):
  • a_stacks.c: using the stack allocator (fixed size records, ordered free())
  • a_slab.c: using the slab allocator (fixed size records, unordered free())
• Examples on using the different (low level) backends (lib link):
  • b_stacks_static.c: stack allocator with static memory allocation (lib link)
  • b_stacks_mixed.c: stack allocator with static memory allocation (lib link)
• Examples on using the different linking/embedding options:
  • l_lib.c: linked as lib (either installed or source tree embedded)
  • l_inc.c: included/inlined (either installed or source tree embedded)