* added regex.gmatch iterator and other fixes
* fixed issues reported by Guldoman
* push strings with fixed len just in case for binary safety
* added limit to regex.gsub and use pushinteger
* added description to regex.gsub limits param
* replaced substitutions regex description for correctness
* ignore negative limits on regex.gsub
Before, if `offset > 1` was used, the match would have failed because
the beginning of the string was never met.
Now we force the beginning of the string to be the one specified by the
offset.
Use regular expressions instead of Lua patterns for find and replace editor commands.
Syntax files can now use regex or Lua patterns as before keeping backward compatibility for plugins.