util: rename from utils, avoid RegExp literal

util: rename from utils, avoid RegExp literal

Rename imports.misc.utils to imports.misc.util for more consistency
(eg, with shell-util).

Also, use the string-based RegExp() constructor rather than a RegExp
literal, since the literal is extremely difficult to parse correctly,
and confuses emacs and probably other editors and thus messes up
autoindentation, etc.

https://bugzilla.gnome.org/show_bug.cgi?id=635089