[compiler-rt] Enhance function padding detection for function interception

Summary:
Many CRT (64-bits) functions contains a "hint-nop". The current padding
detection is not able to recognize the 10-bytes padding and the HotPatch
hooking technique cannot be used.

Other patterns may be discover and may be added later.

Reviewers: rnk

Subscribers: llvm-commits, wang0109, chrisha

Differential Revision: http://reviews.llvm.org/D22258

llvm-svn: 275180