Re-enable UPnP by default in gitian builds

IIRC this was the case with 0.8.6, so let's keep this to avoid the risk
of losing connectable nodes with 0.9 release.

Also our miniupnpc library was recently updated and I've heard
reports that it works better than before now.

contrib/gitian-descriptors/gitian-linux.yml

@@ -48,7 +48,7 @@ script: |
   mkdir -p distsrc
   cd distsrc
   tar --strip-components=1 -xf ../$DISTNAME
-  ./configure --prefix=$STAGING --bindir=$BINDIR --with-protoc-bindir=$STAGING/host/bin --with-boost=$STAGING --disable-maintainer-mode --disable-dependency-tracking PKG_CONFIG_PATH="$STAGING/lib/pkgconfig" CPPFLAGS="-I$STAGING/include ${OPTFLAGS}" LDFLAGS="-L$STAGING/lib ${OPTFLAGS}" CXXFLAGS="-frandom-seed=bitcoin ${OPTFLAGS}" BOOST_CHRONO_EXTRALIBS="-lrt"
+  ./configure --enable-upnp-default --prefix=$STAGING --bindir=$BINDIR --with-protoc-bindir=$STAGING/host/bin --with-boost=$STAGING --disable-maintainer-mode --disable-dependency-tracking PKG_CONFIG_PATH="$STAGING/lib/pkgconfig" CPPFLAGS="-I$STAGING/include ${OPTFLAGS}" LDFLAGS="-L$STAGING/lib ${OPTFLAGS}" CXXFLAGS="-frandom-seed=bitcoin ${OPTFLAGS}" BOOST_CHRONO_EXTRALIBS="-lrt"
   make $MAKEOPTS
   make $MAKEOPTS install-strip
   

contrib/gitian-descriptors/gitian-win.yml

@@ -77,7 +77,7 @@ script: |
     mkdir -p distsrc
     cd distsrc
     tar --strip-components=1 -xf $HOME/build/bitcoin/$DISTNAME
-    ./configure --bindir=$BINDIR --prefix=$STAGING --host=$HOST --with-qt-plugindir=$STAGING/plugins  --with-qt-incdir=$STAGING/include --with-qt-bindir=$STAGING/host/bin --with-boost=$STAGING --disable-maintainer-mode --with-protoc-bindir=$STAGING/host/bin --disable-dependency-tracking CPPFLAGS="-I$STAGING/include ${OPTFLAGS}" LDFLAGS="-L$STAGING/lib ${OPTFLAGS}" CXXFLAGS="-frandom-seed=bitcoin ${OPTFLAGS}"
+    ./configure --enable-upnp-default --bindir=$BINDIR --prefix=$STAGING --host=$HOST --with-qt-plugindir=$STAGING/plugins  --with-qt-incdir=$STAGING/include --with-qt-bindir=$STAGING/host/bin --with-boost=$STAGING --disable-maintainer-mode --with-protoc-bindir=$STAGING/host/bin --disable-dependency-tracking CPPFLAGS="-I$STAGING/include ${OPTFLAGS}" LDFLAGS="-L$STAGING/lib ${OPTFLAGS}" CXXFLAGS="-frandom-seed=bitcoin ${OPTFLAGS}"
     export LD_PRELOAD=/usr/lib/faketime/libfaketime.so.1
     export FAKETIME=$REFERENCE_DATETIME
     make $MAKEOPTS