Update gitian build descriptors to produce proper builds.

Thanks to makomk for finding the bugs here and devrandom
for passing them along (see
https://bitcointalk.org/index.php?topic=42198.msg514312#msg514312)

contrib/gitian-win32.yml

@@ -10,6 +10,7 @@ packages:
 - "unzip"
 - "nsis"
 - "faketime"
+- "wine"
 reference_datetime: "2011-01-30 00:00:00"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"

contrib/gitian.yml

@@ -34,7 +34,7 @@ script: |
   mkdir wxWidgets-2.9.2
   cd wxWidgets-2.9.2
   unzip ../wxWidgets-2.9.2-x32-gitian.zip
-  unzip -f ../wxWidgets-2.9.2-x64-gitian.zip
+  unzip -o ../wxWidgets-2.9.2-x64-gitian.zip
   cp -a bin/$GBUILD_BITS/wx/config/gtk2-unicode-static-2.9 $INSTDIR/bin/wx-config
   for lib in wx_gtk2u wxregexu wxtiff; do
     ar rc $INSTDIR/lib/lib${lib}-2.9.a bin/$GBUILD_BITS/$lib/*.o