Adjust the -path flags in 112 RGL modules

The -path flags in the RGL modules compiled during 'cabal build' now refer 
directly to the needed source directories. References 'alltenses' and 'present'
(and the nonexistent directory 'mathematical') have been removed.

This allows the files to be compiled in any order (e.g. in parallel). In
addition, you can do things like

	gf -retain lib/src/api/TrySwe.gf

without compiling/installing any other RGL modules first, and without 
setting any other path flags or environment variables.

src/english/AllEng.gf

@@ -1,4 +1,4 @@
---# -path=.:../abstract:../common:../api
+--# -path=.:../abstract:../common:../api:../prelude
 
 concrete AllEng of AllEngAbs = 
   LangEng, 

src/english/CompatibilityEng.gf

@@ -1,4 +1,4 @@
---# -path=.:../abstract:../common
+--# -path=.:../abstract:../common:../prelude
 
 concrete CompatibilityEng of Compatibility = CatEng ** open Prelude, ResEng in {
 

src/english/SymbolEng.gf

@@ -1,4 +1,4 @@
---# -path=.:../abstract:../common
+--# -path=.:../abstract:../common:../prelude
 
 concrete SymbolEng of Symbol = CatEng ** open Prelude, ResEng in {