Some PKGBUILD fixes for mate-text-editor and mate-system-tools

Hi,

I've just done a complete build of all the MATE packages in a clean `chroot` using `makerpro`. I've found several that would not build and fixed a couple.

  * `mate-text-editor` requires `enchant` as a build requirement.
  * `mate-system-tools` was missing a linker flag.

Regards, Martin.