Fix missed exception spec checks and crashes

Delayed exception specification checking for defaulted members and virtual
destructors are both susceptible to mutation during iteration so we need to
process the worklists fully.

This resolves both accepts-invalid and rejects-valid issues and moreover fixes
potential invalid memory access as the contents of the vectors change during
iteration and recursive template instantiation.

This patch also adds two assertions at end of TU to ensure no specs are left
unchecked as was happenning before the fix, plus a test case from Marshall Clow
for the defaulted member crash extracted from the libcxx headers.

Reviewed by Richard Smith.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192914 91177308-0d34-0410-b5e6-96231b3b80d8
Make .asm a valid extension for assembly files

This is a common extension on Windows, and now clang will assemble them
instead of treating them as linker input which is the default for unknown
file types.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192919 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Fix missed exception spec checks and crashes"

The changes caused the sanitizer bot to hang:
  http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/2311

Needs investigation.

This reverts commit r192914.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192921 91177308-0d34-0410-b5e6-96231b3b80d8
[ms-cxxabi] Error out on virtual function memptrs

These are uncommon and this is better than miscompiling.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192923 91177308-0d34-0410-b5e6-96231b3b80d8