-fglasgow-exts for -syslib lang
Toying around with the module IArray from -syslib lang, Gabi and I found that we need to give ghc -fglasgow-exts, because IArray is a multi-parameter type class. This is a problem, because a user less familar with ghc, will probably not be able to infer from some strange error message whose position is in ArrayBase.hi what the problem is. This suggests that the driver should automatically add -fglasgow-exts when -syslib lang is specified. The problem with this strategy is, however, that also when somebody imports components of -syslib lang that do not need extensions, the flag will be used. So, maybe we should split lang into lang-h98 and lang-exts or so. At the very least, the documentation for IArray should mention this caveat.