The System-V x86_64 ABI requires floating point values to be passed in 128-but SSE vector registers (xmm0, ...).
When printing such a variable this currently yields an <invalid load address>.
This patch makes LLDB's DWARF expression evaluator accept 128-bit registers as scalars. It also relaxes the check that the size of the result of the DWARF expression be equal to the size of the variable to a greater-than. DWARF defers to the ABI how smaller values are being placed in a larger register.
Implementation note: I found the code in Value::SetContext() that changes the m_value_type after the fact to be questionable. I added a sanity check that the Value's memory buffer has indeed been written to (this is necessary, because we may have a scalar value in a vector register), but really I feel like this is the wrong place to be setting it.