Welcome to LQ.
'glib >= 2.4' means a glib later than version 2.4 ( Or 2.4 )
Glib2 is already installed : ls /var/log/packages/ | grep glib-2
( It is 'glib2-2.22.5' in Slackware 13.1 ).
Please do : cd glib-2.4/ ; # make uninstall :
You don't need a seven year old glib2.
Also please : cd pkg-config-<version>/ ; # make uninstall
( Slackware 13.1 has pkg-config-0.23 already.)
All the mono packages for Slackware are here
http://slackbuilds.org/result/?search=mono&sv=13.1
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