allow user actions in debug mode

[chdelfosse]

I suggest to add a one line mod (actually addition)
"lexobj.lexdebug=debug"
at line 980 of lex.py

in order to allow a line ( in a lex user rule)
if t.lexer.lexdebug:
print("beginning %s"%t.lexer.FUTURE)

the functional code would NOT be impacted
the suggested element begins with 'lex'

[chdelfosse]

the user lex code should have read (to make the purpose clearer):
if t.lexer.lexdebug:
print("beginning %s"%t.lexer.FUTURE)
t.lexer.begin(t.lexer.FUTURE)