Add support for defining macros with arguments with -DFOO(X)=X.

This would be useful for eg:

$ ./pike '-D_refs(X)=3' .../some/old/version/socktest.pike

Currently only -DFOO=3 and -DFOO()=3 are supported. Note that the syntax -DFOO(X)=X is accepted, but defines a macro with the name FOO(X)...

The reasonable place to implement this is cpp.cmod:add_define().