[hwasan] Provide __sanitizer_* aliases to allocator functions.

Summary:
Export __sanitizer_malloc, etc as aliases to malloc, etc.
This way users can wrap sanitizer malloc, even in fully static binaries.

Both jemalloc and tcmalloc provide similar aliases (je_* and tc_*).

Reviewers: vitalybuka, kcc

Subscribers: llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D50570

llvm-svn: 339614