Merging r243098, r243101, r243105, r243144, and r243153.

Merging r243098, r243101, r243105, r243144, and r243153.

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r243098 | yrnkrn | 2015-07-24 01:50:15 -0700 (Fri, 24 Jul 2015) | 7 lines

Add extensive tests for the mingw toolchain and remove trailing slash from Arch.

Address Richard Smith comments: remove the trailing seperator from the Arch
variable, implement six mingw_* trees under tools/clangtest/Driver/Inputs
and merge linux and Windows tests into a universal test that uses these trees.
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r243101 | yrnkrn | 2015-07-24 02:31:57 -0700 (Fri, 24 Jul 2015) | 3 lines

Try to appease clang buildbot by forcing libstdc++ in mingw.cpp test.
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r243105 | yrnkrn | 2015-07-24 04:01:45 -0700 (Fri, 24 Jul 2015) | 4 lines

Apparently some of the bots add .svn dirs inside the test/Driver/Inputs
directory structure. Try to make mingw toolchain resilient to such surprises.
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r243144 | yrnkrn | 2015-07-24 12:18:17 -0700 (Fri, 24 Jul 2015) | 5 lines

Base the sys-root/mingw/include path on sysroot and not on /usr.

Thanks to Richard Smith for pointing this out!
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r243153 | yrnkrn | 2015-07-24 13:18:27 -0700 (Fri, 24 Jul 2015) | 4 lines

Select the highest version of the mingw toolchain found using Generic_GCC::GCCVersion
similar to the way Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple works.
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_37@243325 91177308-0d34-0410-b5e6-96231b3b80d8