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.