[Make it clear that 'progCombMap' is just a cache.
Lemmih <lemmih@gmail.com>**20081127132322
 Ignore-this: cadc5efe5c1bc8c39fccff75418e9f33
] hunk ./E/Program.hs 45
-    progCombMap        :: IdMap Comb,
+    progCombMap        :: IdMap Comb,  -- progCombMap is always (fromList . progCombinators)