Merge RegisterContextPOSIX_x86_64 and RegisterContextPOSIX_i386 into RegisterContextPOSIX_x86

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@192332 91177308-0d34-0410-b5e6-96231b3b80d8
Fixed a leak of ASTStructExtractors and also
made sure we don't keep around no-longer-valid
ASTTransformers.

<rdar://problem/15182379>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@192333 91177308-0d34-0410-b5e6-96231b3b80d8