grammar.py and friends: Make list parsing run through

First time parsing doesn't error out with a syntax error. No usable AST
is produced, strings are not returned from lexer, and AST lists aren't
lists, really.

TEXT:="Hello world!"; had to be excluded from the example, because I
don't get how this could be parsed with the given syntax. There's a
special sequence "all visible characters", but any lexer regex I could
think of will also match the types defining "alphabetic character" and
return the respective tokens (e.g. T_A) or vice-versa, depending on the
order in the lexer input file. I suppose, the only sensible way to
handle this, is to define "all visible characters" by defining the
tokens for the missing characters, and then use them along T_A ... T_Z
or their derived types.

Signed-off-by: Jan Lindemann <jan@janware.com>

test/grammar/grammartest.code

@@ -6,5 +6,4 @@ BEGIN
   C:=A;
   D123:=B34A;
   BABOON:=GIRAFFE;
-  TEXT:="Hello world!";
 END.