Fix a bug in mutex_try_to_lock.  This was previously trying to unlock a mutex that it didn't own, causing an assertion failure in mutex.cpp.  The issue was that the unique_lock went out of scope, releasing the lock on m, then m.unlock() was called on an already-unlocked mutex.

This change removes the spurious m.unlock() call.

If this test was previously passing for anyone with assertions enabled, then they should investigate bugs in their pthread implementation, as pthread_unlock() should not return 0 if the mutex is currently unlocked.
[asan] instrument memory accesses with unusual sizes

This patch makes asan instrument memory accesses with unusual sizes (e.g. 5 bytes or 10 bytes), e.g. long double or
packed structures.
Instrumentation is done with two 1-byte checks
(first and last bytes) and if the error is found
__asan_report_load_n(addr, real_size) or
__asan_report_store_n(addr, real_size)
is called.

Also, call these two new functions in memset/memcpy
instrumentation.

asan-rt part will follow.