[sanitizer] Include inlined frames into __sanitizer_symbolize_pc output

Summary:
Behavior for existing used is not changing as the first line is going
to be the same, and it was invalid to try to read more lines.

New clients can read until they get empty string.

Reviewers: eugenis, morehouse

Subscribers: kubamracek, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D52743

llvm-svn: 343554