eclass/ghc-package.eclass: add 'ghc-supports-interpreter()'

For 'ghci' or 'template-haskell' detection.
dev-haskell/matrix: new package (dep for hatex asked by romildo)

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
dev-haskell/hatex: new package (asked by romildo)

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>