build: Quagga 0.99.23-rc1

this is not a full release version, so neither release notes nor
documentation are updated yet.  Also, signing the tag with my private
GPG key instead of the Quagga one.
diff --git a/configure.ac b/configure.ac
index f9b1763..fa9e6e1 100755
--- a/configure.ac
+++ b/configure.ac
@@ -7,7 +7,7 @@
 ##
 AC_PREREQ(2.53)
 
-AC_INIT(Quagga, 0.99.22, [https://bugzilla.quagga.net])
+AC_INIT(Quagga, 0.99.23-rc1, [https://bugzilla.quagga.net])
 AC_CONFIG_SRCDIR(lib/zebra.h)
 AC_CONFIG_MACRO_DIR([m4])