lualoader: position hyphens at the beginning of character classes

According to the Lua 5.4 manual section 6.4.1 ("Patterns"), the interaction
between ranges and classes is not defined and hyphens must be specified at
either the beginning or the end of a set if they are not escaped.

Move all such occurrences to the beginning.

Reported-by: _parv (twitter)
MFC-after: 3 days