fix regular expression for ANSI escapes

wouldn't catch `\x1b[01;`, only `\x1b[0;` or `\x1b[1;`.

closes #3614
Merge pull request #3615 from minrk/ansilinux

Fix regular expression for ANSI escapes, which wouldn't catch `\x1b[01;`, only `\x1b[0;` or `\x1b[1;`.

Closes #3614.