Don't include pthread.h when it's not needed.

Fixes mingw-w64 build.

This commit is licensed under MIT/X11.
Merge pull request #694 from madewokherd/pthreadinclude

Don't include pthread.h when it's not needed.
[build]: Use a relative symlink from mono to mono-sgen.
Bump libmonosgen version in the .spec file.
[runtime]Revert the fast tls check as we always need it on mach. Add another iOS 7 offset.
Use a non rooted symlink and make it point to the right mono.
Ensure the new FileStream unit tests does not throw in the non-main thread (which nunit-console won't report but other tools, like Touch.Unit, will)
Fix preprocessor/compiler warning due to unbalanced apostophe (') character

Reworded the warning message to be displayed when the fall-through case is taken by the preprocessor in `mono_thread_get_stack_bounds()`.
Merge pull request #695 from jack-pappas/patch-4

Fix preprocessor/compiler warning due to unbalanced apostophe (') character
configure: Set TARGET=S390X instead of S390x for consistency.
Add atomic.c/.h to libmonoutils.vcxproj.