Support escaped octal and hexadecimal characters in regular expressions
Support escaped octal and hexadecimal characters in regular expressions

In the previous commit, we did not support characters in regular
expressions specified via \0..., \x... or \u... yet. This is a bit more
involved, therefore support for them is added in its own commit.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>

getlantern/avian,lwahlmeier/avian,getlantern/avian,lostdj/avian,joshuawarner32/avian,getlantern/avian,minor-jason/avian,ucdseniordesign/avian,MaartenR/avian,joshuawarner32/avian,bigfatbrowncat/avian-pack.avian,lwahlmeier/avian,getlantern/avian,joshuawarner32/avian,lwahlmeier/avian,MaartenR/avian,minor-jason/avian,marcinolawski/avian,bgould/avian,ucdseniordesign/avian,dicej/avian,lwahlmeier/avian,joshuawarner32/avian,minor-jason/avian,bgould/avian,minor-jason/avian,bgould/avian,dicej/avian,marcinolawski/avian,bgould/avian,lostdj/avian,bigfatbrowncat/avian-pack.avian,lostdj/avian,MaartenR/avian,dicej/avian,dicej/avian,MaartenR/avian,ucdseniordesign/avian,marcinolawski/avian,marcinolawski/avian,lostdj/avian,bigfatbrowncat/avian-pack.avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian