Lower required version of sqlite

We've really only tested 3.8.3.1, so you might want to consider using
that.  We'll lower this down to 3.7.13 for Debian wheezy.  Please
test.

configure.ac

@@ -1081,7 +1081,7 @@ case $host in
        ;;
 esac
 
-PKG_CHECK_MODULES([SQLITE], [sqlite3 >= 3.8.3.1])
+PKG_CHECK_MODULES([SQLITE], [sqlite3 >= 3.7.13])
 PKG_CHECK_MODULES([CURL], [libcurl >= 7.19])
 PKG_CHECK_MODULES([PCRE], [libpcre >= 7.8])
 PKG_CHECK_MODULES([SPEEX], [speex >= 1.2rc1 speexdsp >= 1.2rc1])