Add options for GModule to config.jnaerator

GModule has its own shared library (libgmodule-2.0.so on Linux).
The generated bindings know the name of the shared library where
the native functions are located by the -library JNAerator option.
This commit modifies config.jnaerator to have JNAerator parse
gmodule.h under the effect of the appropriate -library option. This
solves 8 BridJ warnings when running the GList test, and should
make GModule usable through the generated bindings.