[ new ] added commonPrefix and commonSuffix to Utils.List
[ refactor ] moved literal pretty instance to Literal module
[ new ] pure pretty printer for internal syntax

The (derived) show instance for is really horrible to read. Sometimes
you are in a position where you don't have access to prettyTCM but you
still want readable terms for debugging.
[ test ] fixed bugs in commonPre/Suf properties
[ new ] added countTelVars to count bindings in a concrete telescope
[ issue892 ] fixed

Required a slight change in the semantics of module application.
Previously re-exported functions were not redefined in the new module,
but simply aliased by the scope checker. This is wrong as issue 892
shows, so now all exported functions are redefined, which may lead to
ambiguous identifier errors in code that previously checked.
[ issue892 ] another test case
Merge branch 'issue892'