Adding "Contributing to the MPS" that will show up on GitHub pull requests.
Adding symlink from CONTRIBUTING to contributing.rst to make it easier to find for people used to the GNU conventions.
Fixing grammar problem in MPS contributions agreement.
Adding link to guide.impl.c.format.
Don't define _GNU_SOURCE if already defined.

When using the build method of including the MPS directly into
one's own sources, that build system may already define _GNU_SOURCE
causing a warning here about re-defining it.
Fix typo: it's MPS_BUILD, not MPS_BUILDER.
Merging branch/2013-06-18/macosx-threads back to master.
Adding missing #endif caused by merge error.  Oops.
Added note about why we don't check that we're the only exception port before sending a reply.
Bring release notes up to date.
It's no longer necessary to build the manual, but it is necessary to update the release notes.
Avoid calling abort() on Windows when running the test suite, so that the test suite doesn't get suspended waiting for someone to press a button.
Improve reporting of test failures on Windows, so that the continuous integration is helpful.
Three test cases assumed that MPS_PF_ALIGN is always equal to sizeof(void *), but this isn't true on platform w3i3mv where sizeof(void *) is 4 and MPS_PF_ALIGN is 8. Remove the assumption from these test cases.
Correct PASS_COUNT to FAIL_COUNT in testrun.bat.
locbwcss shouldn't fail if there are non-contiguous allocations. Those are perfectly legitimate (MVFF uses CBS, which needs to allocate nodes in its splay tree).
Fixing sacss failure introduced in changelist 183045.  Alignments are unpacked from varargs as promoted to size_t, but MPS_PF_ALIGN is a naked number literal, and so was passed as int, causing a corrupt alignemnt failure in sacss.
Improve allocation example so that it demonstrate aligning up the size. Explain why the MPS doesn't do this for you. Fix typo in scanning chapter.
Clarifying why AP protocol loops are very rare.
Document AP creation requirements in terms of mps_ap_create_k, not the deprecated mps_ap_create.
Fixing mentions of mps_size_t to just size_t in the manual.  The former doesn't exist.
PROT_SIGINFO_GOOD and PROT_SIGNAL are no longer needed on OS X.