Range checks for operator DIV and MINUS were incorrect
as reported by Alexandre Esteves

Don't do anything at elaboration

the Makefile.Python would not regenerate dataview-uniq.h if the file is
already there, but for the python backends we must not have the asn1scc
prefixes

Report error when user writes somechoice!a := value instead of
somechoice := a:value (reported warning before)
and report no error when accessing somechoice!a (on the right side of
expressions)
Add test case