eliminate malloc hashtable

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on February 23, 2012 15:09:50_

xref general case issue #460 first we should establish that the malloc hashtable is indeed a bottleneck with the other issue #460 opts are there and once drwrap is as fast as the dedicated impl ( issue #689 )

in my original DrMem code I didn't use a malloc hashtable b/c leaks were
off by default. the table is used to iterate allocs for leaks, to store
callstacks, to identify pre-us and native (LFH tangent) allocs, and for
alloc mismatch detection.

**\* TODO store data in redzone and do Rtl heap iterate for leak scan

store callstacks and mismatch flags in redzone

for pre-us: no hashtable, have magic value, if hits also call RtlHeapSize
to be sure it's pre-us.

for pattern, where can't store in redzone: have rbtree anyway.

**\* TODO get rid of hashtable and replace w/ alloc history

Qin's idea:
per-thread buffer that stores rdtsc
merge often enough to avoid rdtsc rollover
would that be faster than hashtable?

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=793_