Use only one FindCplex.cmake

[chaubold]

Currently there's a FindCplex.cmake in martinsch/buildem and in pgmlink. I ran into the problem that they were out of sync, and thus it didn't find all libraries. (See 29faad50cd25dd20d75863bdbfd4ba284a76dbd3)

Regarding that one might want to compile pgmlink without buildem, what would be the best workaround for this?

• set the cmake_module_path in pgmlink to buildem if buildem_dir is set and use a symlink for the one in pgmlink locally?

[martinsch]

In general, pgmlink is built without buildem. So, this is fine.