rdar://problem/10611315

expression command doesn't handle xmm or stmm registers...

o Update ClangASTContext::GetBuiltinTypeForEncodingAndBitSize() to now handle eEncodingVector.

o Modify RegisterValue::SetFromMemoryData() to fix the subtle error due to unitialized variables.

o Add a test file for "expr $xmm0".

llvm-svn: 152190