memintercept.c: Intercept calls to the WebKit allocator routines

memintercept.c: Intercept calls to the WebKit allocator routines

Allow to intercept calls to WebKit's WTF::fastMalloc and
track malloc/free usage of it. This is still C code that
is following the C++ name mangling and will only work on
systems following the Common Vendor ABI. This limitation
is good enough right now.

The WebKit allocator (TCmalloc) is still used when fastMalloc
is called which allows to look at memory fragmentation
with the real allocator.

* lib/memintercept.c:
(_ZN3WTF10fastMallocEj): Add WTF::fastMalloc(unsigned int)
(_ZN3WTF11fastReallocEPvj): Add WTF::fastRealloc(void *, unsigned int)
(_ZN3WTF8fastFreeEPv): Add WTF::fastFree(void)
(_ZN3WTF10fastCallocEjj): Add WTF::fastCalloc(unsigned int, unsigned int)
(mi_init): Look for fastMalloc and such