Added an Xcode target so we build the "lldb-mi" executable as part of the...

Added an Xcode target so we build the "lldb-mi" executable as part of the "desktop" and "desktop no xpc" targets.

Include paths were switched to be user include paths, if this breaks the linux build we will need to fix the Makefiles/cmake stuff.

<rdar://problem/19198581> 

llvm-svn: 226530