[Sanitizer/ASan] Simplify the code that prints and symbolizes stack traces. Fall...

[Sanitizer/ASan] Simplify the code that prints and symbolizes stack traces. Fall back to module+offset if user-provided symbolizer failed. Use weak function __asan_symbolize instead of __asan_set_symbolize_callback in ASan interface, so that we're able to symbolize reports for errors that happen before the main() is called, for example, during module initialization.

llvm-svn: 165000