gstinfo.[ch], cothreads.c: added initial support for -finstrument_functions gstbin...

gstinfo.[ch], cothreads.c: added initial support for -finstrument_functions gstbin.c: removed a reference to config.h...

Original commit message from CVS:
gstinfo.[ch], cothreads.c: added initial support for -finstrument_functions
gstbin.c: removed a reference to config.h
gstbuffer.[ch]: added gst_buffer_is_span_fast(), used it in gst_buffer_span
elements/gstfilesrc.c: initial work fleshing out the event handling code

everywhere else: wrapped XML stuff in #ifndef's