ADT: remove MinGW32 and Cygwin OSType enum

Remove the MinGW32 and Cygwin types from the OSType enumeration.  These values
are represented via environments of Windows.  It is a source of confusion and
needlessly clutters the code.  The cost of doing this is that we must sink the
check for them into the normalization code path along with the spelling.

Addresses PR20592.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215303 91177308-0d34-0410-b5e6-96231b3b80d8
If available, pass down the Fixup object to EvaluateAsRelocatable.
At least on PowerPC, the interpretation of certain modifiers depends on
the context they appear in.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215310 91177308-0d34-0410-b5e6-96231b3b80d8
Fix tabs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215311 91177308-0d34-0410-b5e6-96231b3b80d8