Add Documentation to Regexp
Documented non-subexp option toggling
Regexp option toggling can be done in two forms:
/(?imx:subexpr)/ - this was already mentioned in docs
/before(?imx)after/ - there was no mention of this.
This section of the documentation could be improved further, see the following from the Onigmo docs:
(?imxdau-imx) option on/off i: ignore case m: multi-line (dot(.) match newline) x: extended form character set option (character range option) d: Default (compatible with Ruby 1.9.3) \w, \d and \s doesn't match non-ASCII characters. \b, \B and POSIX brackets use the each encoding's rules. a: ASCII ONIG_OPTION_ASCII_RANGE option is turned on. \w, \d, \s and POSIX brackets doesn't match non-ASCII characters. \b and \B use the ASCII rules. u: Unicode ONIG_OPTION_ASCII_RANGE option is turned off. \w (\W), \d (\D), \s (\S), \b (\B) and POSIX brackets use the each encoding's rules.