[ Epic ] Replaced 'pretty' by 'prettyShow'

See https://github.com/agda/agda/commit/33daa06a435c40b49d8cb7051e7fec8dc10f5a49#commitcomment-8046035
Merge branch 'maint-2.4.2'
[ issue 1284 ] Added -fwarn-missing-signatures flag to some modules
Merge branch 'maint-2.4.2'
Merge remote-tracking branch 'upstream/master'