Somehow transfer comments from .gob to .h and .c files to make gtk-doc
possible.  Alternatively make gob act as gtk-doc, or generate a gtk-doc
ready stub file.

.defs file generation

signal RUN_ flags.  Auto add GTK_RUN_ACTION for public signals, but add
a way to specify other flags

a connect_full function for each signal with typesafe function pointer
argument and macros for the other (simpler) connect types.