m4/atheme-print-configuration: make even nicer output

m4/atheme-print-configuration: make even nicer output

Group lines by category, indent them some more, indicate which SASL
mechanisms are going to be built (some are always built, so this output
won't change, but they're just there for consistency's sake...).

Good news for all of those stuck in 1995: Aside from the build variables
(CC/CFLAGS/CPPFLAGS/LDFLAGS/LIBS), it all still fits into 80 columns, so
your VGA console can render it just fine.