Those are the "dev" files, the lib has to be there somewhere (I'm not at a tc machine at the moment) - in /usr/lib as opposed to /usr/local/lib maybe?
Note that libXinerama.so.1 will mostly likely be a symlink, you will need all the libXinerama.so* files.
Edit: with the version of Xorg-7.4 I have: $ ls /usr/local/lib/libXin*
/usr/local/lib/libXinerama.so
/usr/local/lib/libXinerama.so.1
/usr/local/lib/libXinerama.so.1.0.0
Note that there's no libXinerama.a/la - did you maybe load Xorg-7.4-dev in error?