common.cmake: force CMake to use .so suffix for plug-ins
cl: remove unnecessary system header includes

... which were breaking compilation on Darwin
gcc: eliminate an unsafe use of basename()

basename() uses a static storage on Darwin, which caused Code Listener
to print unrelated strings in diagnostic messages.
sl: do not chain references, it breaks old GCCs
slgcc: avoid calling mktemp(1) without a template

It does not work on Darwin.
predator-regre: remove unnecessary header includes

... which were breaking the test-suite on Darwin