This adds support for character classes such as \d or \W, leaving \p{...}
style character classes as an exercise for later.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This will be used to match character classes (such as '[0-9a-f]'),
but it will also be used by the regular expression pattern compiler
to determine whether a character has special meaning in regular
expressions.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
