bump product version to 7.3.0.0.alpha0+

Change-Id: I22adfa913dad2a4ae5d6fbeab87daf22f5545282
diff --git a/configure.ac b/configure.ac
index 7fc0360..63dc5ef 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,7 +9,7 @@ dnl in order to create a configure script.
# several non-alphanumeric characters, those are split off and used only for the
# ABOUTBOXPRODUCTVERSIONSUFFIX in openoffice.lst. Why that is necessary, no idea.

AC_INIT([LibreOffice],[7.2.0.0.alpha1+],[],[],[http://documentfoundation.org/])
AC_INIT([LibreOffice],[7.3.0.0.alpha0+],[],[],[http://documentfoundation.org/])

dnl libnumbertext needs autoconf 2.68, but that can pick up autoconf268 just fine if it is installed
dnl whereas aclocal (as run by autogen.sh) insists on using autoconf and fails hard