.cabal: fix depends for 'cabal configure -fbuildtests'

$ cabal configure -fbuildtests
$ cabal build

Database/HDBC/SqlValue.hs:25:17:
    Could not find module `Data.Text.Lazy':
      It is a member of the hidden package `text-0.11.0.6'.
      Perhaps you need to add `text' to the build-depends in your .cabal file.
      Use -v to see a list of the files searched for.

Added missing depend for test.

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

HDBC.cabal

@@ -68,7 +68,7 @@ Executable runtests
           Build-Depends: time<1.1.3
       else
         Build-Depends: base<3
-      Build-Depends: mtl, convertible >= 1.0.9.1, utf8-string
+      Build-Depends: mtl, convertible >= 1.0.9.1, utf8-string, text
 
       -- Hack for cabal-install weirdness.  cabal-install forces base 3,
       -- though it works fine for Setup.lhs manually.  Fix.