Fix #5720 - puppetdoc misses some class comments

It appears that the fix for #5252 wasn't complete, and class, nodes and
definition were still using the current lexer line number instead of
the line number of the class/define/node token.
This combined with some missing comments stack pushing/pop on parenthesis
prevented puppetdoc to correctly get the documentation of some class (including
parametrized ones).

Signed-off-by: Brice Figureau <brice-puppet@daysofwonder.com>