Split libc_debug.so into two .so modules loaded on demand from libc.so

This change is intended to eliminate need to replace libc.so with libc_debug.so in order to enablememory allocation debugging.
This is also the first step towards implementing extended memoryallocation debugging using emulator's capabilities in monitoring memory access.

libc/bionic/libc_init_static.c

@@ -68,12 +68,6 @@ __noreturn void __libc_init(uintptr_t *elfdata,
     /* Initialize the C runtime environment */
     __libc_init_common(elfdata);
 
-#ifdef MALLOC_LEAK_CHECK
-    /* setup malloc leak checker, requires system properties */
-    extern void malloc_debug_init(void);
-    malloc_debug_init();
-#endif
-
     /* Several Linux ABIs don't pass the onexit pointer, and the ones that
      * do never use it.  Therefore, we ignore it.
      */