Make static counters in ASTContext non-static.
Summary:
Fixes a data race and makes it possible to run clang-based tools in
multithreaded environment with TSan.
Reviewers: ilya-biryukov, riccibruno
Reviewed By: riccibruno
Subscribers: riccibruno, jfb, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D58612
llvm-svn: 354795