libircclient-1.6-install.patch allows running make install and use libdir and includedir in case it is not standard. Usually only libdir can have a value other than @prefix@/lib/.
libircclient-1.6-rfc.patch is required at least when building megaglest, to avoid an error like:
error: 'LIBIRC_RFC_RPL_ENDOFNAMES' was not declared in this scope
If building a shared library, I believe it would be desirable to use a major for it. Since Makefile.in is hand made, it could be done with something like:
- $(CC) -shared -s -o libircclient.so libircclient.o @LIBS@
+ $(CC) -shared -s -o libircclient.so.0 -Wl,-soname=libircclient.so.0 libircclient.o @LIBS@
+ ln -s libircclient.so.0 libircclient.so
and then update the install patch.