library adjustments, error message clean-up

examples/gfcc/ImperJVM.gf

@@ -1,4 +1,4 @@
---# -path=.:../prelude
+--# -path=.:../../lib/prelude
 concrete ImperJVM of Imper = open ResImper in {
 
 flags lexer=codevars ; unlexer=code ; startcat=Stm ;