Update to 2.8.14.

This fixes a bug in the brush tool [1]
Use new GIMP master site macro.
Drop :keepla from USES=libtool
Remove intltool, libartlgpl2 and gnomehier from USE_GNOME.

Intlhack already implies intltool, gnomehier is obsolete now that pkg
handles directories and libartlgpl2 is unused.

PR: 194532 [1]
Submitted by: Kalten <kalten@gmx.at> [1]