#47 Implement regular expressions

[Andrei Kapustin]

Implement search/replace for regular expressions. Use the ones from Perl as a base (seems to be the most comprehensive ones).

[Andrei Kapustin]

Update: C++ now has regex support, so use it across all platforms.

Generalize to "pattern matching", which allows matching strings to patterns. One kind of patterns are regexes, another a OS-style globs (with ? and *). This done, the directory and file dialog filters can be switched to use the "glob pattern matcher").