libc: Add an implementation of strtol/strtoul and export it via plugins

These were lifted from the lua plugin.

sdl, doom, puzzles updated to use the exported version

todo: lua, maybe?
also: convert uses of atoi [back] to strtol

Change-Id: I5a1ebbe8d8c99349e594ab9bbbce474e7645b4e9

apps/plugins/lua/rocklib_aux.pl

@@ -51,6 +51,8 @@ my @ported_functions;
 # you want to manually port them to Lua. The format is a standard Perl regular
 # expression.
 my @forbidden_functions = ('^atoi$',
+                           '^strtol$',
+                           '^strtoul$',
                            '^open$',
                            '^open_utf8$',
                            '^close$',