Fix flags so that they work for mac and non-mac.

It is duplicating stuff to put -g in for debug builds, that flag for GCC compilers should be put in by the relevant specs file for the debug builds (as is the -03 for the optimised release build).  I found the -Wno-deprecated-declarations was required for building the (version 0.5.0) irc library, but perhaps they will go away if we source and include a later version (http://communi.github.io/ currently is at 3.2.0) though I do not recall whether -Wno-deprecated is a superset that include the more explicit existing flag.