Revert 238913 "Make gtest always use simple internal regex engine."

Breaking base_unittests on a number of bots:
http://build.chromium.org/p/chromium.mac/builders/Mac%2010.6%20Tests%20%28dbg%29%283%29/builds/44666
http://build.chromium.org/p/chromium.linux/builders/Linux%20Clang%20%28dbg%29/builds/54034
http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/27229
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASAN%20Tests%20%281%29/builds/21675
http://build.chromium.org/p/chromium.memory/builders/Mac%20ASAN%2064%20Tests%20%281%29/builds/216

> Make gtest always use simple internal regex engine.
> 
> In order to allow regex matches in gtest to be shared between Windows and other
> systems, we tell gtest to always use it's internal engine.
> 
> The syntax supported by the internal engine initially looks like a subset of
> POSIX regexs. However character class shortcuts are not valid POSIX.
> 
> Even more confusingly the system POSIX regex function often defines extra
> features not actually part of the standard allowing regex that work on Linux
> fail on Mac OS X.
> 
> A search through the code base did not reveal any locations where features not
> supported by the internal regex engine where used.
> 
> See bug https://code.google.com/p/chromium/issues/detail?id=317224 for more detailed description.
> 
> BUG=317224
> 
> Review URL: https://codereview.chromium.org/55983002

TBR=mithro@mithis.com

Review URL: https://codereview.chromium.org/100313003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238918 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238918