Implement support for dependent Microsoft __if_exists/__if_not_exists
statements. As noted in the documentation for the AST node, the
semantics of __if_exists/__if_not_exists are somewhat different from
the way Visual C++ implements them, because our parsed-template
representation can't accommodate VC++ semantics without serious
contortions. Hopefully this implementation is "good enough".

llvm-svn: 142901
21 files changed
tree: 6d51e5336be7c931aed6c37a45227e981d076a87
  1. clang/
  2. compiler-rt/
  3. debuginfo-tests/
  4. libcxx/
  5. libcxxabi/
  6. lldb/
  7. llvm/
  8. polly/