Use a new define, NO_XPC_SERVICES, to indicate that macosx/Host.mm

shouldn't compile any of the XPC support code.  

Update macosx/Host.mm to use that define.

Add a LLDB_DISABLE_PYTHON ifdef block around a new function in 
Core/FormatManager.cpp.

<rdar://problem/10942125>

llvm-svn: 152293