[windows] Fix or XFAIL remaining portable test failures and enable them

Summary:
This involved various fixes:

- Move a test that uses ulimit to Posix.

- Add a few "REQUIRES: shell" lines to tests using backtick subshell
  evaluation.

- The MSVC CRT buffers stdio if the output is a pipe by default. Some
  tests need that disabled to avoid interleaving test stdio with asan
  output.

- MSVC headers provide _alloca instead of alloca (go figure), so add a
  portability macro to the two alloca tests.

- XFAIL tests that rely on accurate symbols, we need to pass more flags
  to make that work.

- MSVC's printf implementation of %p uses upper case letters and doesn't
  add 0x, so do that manually.

- Accept "SEGV" or "access-violation" reports in crash tests.

Reviewers: samsonov

Subscribers: tberghammer, danalbert, llvm-commits, srhines

Differential Revision: http://reviews.llvm.org/D12019

llvm-svn: 245073