Update PGF API documentation link on home page, bump version number in gf.cabal to 3.7.1-darcs

gf.cabal

@@ -1,5 +1,5 @@
 name: gf
-version: 3.7.1
+version: 3.7.1-darcs
 
 cabal-version: >= 1.10
 build-type: Custom

index.html

@@ -84,7 +84,7 @@ function sitesearch() {
   </ul>
   <h4>Develop Applications</h4>
   <ul>
-    <li><a href="http://hackage.haskell.org/package/gf-3.7/docs/PGF.html">PGF library API (Haskell)</a>
+    <li><a href="http://hackage.haskell.org/package/gf-3.7.1/docs/PGF.html">PGF library API (Haskell)</a>
     <li><a href="doc/python-api.html">PGF library API (Python)</a>
     <li><a href="src/ui/android/README">GF on Android (new)</a>
     <li><A HREF="/android/">GF on Android (old) </A>