This commit update gimp the latest version and adds its new dependencies

Stable moduleset updates

• gnumake 4.2.1 added to bootstrap to fix webkit parallel build
• gettext-tools, gettext-runtime: upstream patches added
• libxslt: 1.1.32
• gtk-doc: 1.28
• freetype: 2.9.1
• fontconfig: 2.13.0
• gnutls: 3.5.18, glib added as dependency
• libwebp: 1.0.0
• webkit: unbreak parallel builds
• fix broken repository links
• python: 2.7.15
• pygobject: 2.28.7
• python-six: 1.11.0 (added)
• shared-mime-info: 1.9
• GIMP and GIMP-only dependencies removed to move them to separate repository
• gtk+: 2.24.32, new upstream patches
• cairomm: 1.15.5
• cairo: 1.16.0

fixes

• iso-codes: update checkout dir