Lower library version requirement if you choose to use libmaxminddb,

from 1.6.0 to 1.4.3. Suggested by robert-scheck in
https://github.com/unrealircd/unrealircd/pull/183

autoconf/m4/unreal.m4

@@ -397,7 +397,7 @@ AC_DEFUN([CHECK_LIBMAXMINDDB],
 	[
 		dnl see if the system provides it
 		has_system_libmaxminddb="no"
-		PKG_CHECK_MODULES([LIBMAXMINDDB], [libmaxminddb >= 1.6.0],
+		PKG_CHECK_MODULES([LIBMAXMINDDB], [libmaxminddb >= 1.4.3],
 		                  [has_system_libmaxminddb=yes])
 		AS_IF([test "x$has_system_libmaxminddb" = "xyes"],
 		[

configure

@@ -8772,12 +8772,12 @@ if test -n "$LIBMAXMINDDB_CFLAGS"; then
     pkg_cv_LIBMAXMINDDB_CFLAGS="$LIBMAXMINDDB_CFLAGS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmaxminddb >= 1.6.0\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "libmaxminddb >= 1.6.0") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmaxminddb >= 1.4.3\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libmaxminddb >= 1.4.3") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_LIBMAXMINDDB_CFLAGS=`$PKG_CONFIG --cflags "libmaxminddb >= 1.6.0" 2>/dev/null`
+  pkg_cv_LIBMAXMINDDB_CFLAGS=`$PKG_CONFIG --cflags "libmaxminddb >= 1.4.3" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -8789,12 +8789,12 @@ if test -n "$LIBMAXMINDDB_LIBS"; then
     pkg_cv_LIBMAXMINDDB_LIBS="$LIBMAXMINDDB_LIBS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmaxminddb >= 1.6.0\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "libmaxminddb >= 1.6.0") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libmaxminddb >= 1.4.3\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libmaxminddb >= 1.4.3") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_LIBMAXMINDDB_LIBS=`$PKG_CONFIG --libs "libmaxminddb >= 1.6.0" 2>/dev/null`
+  pkg_cv_LIBMAXMINDDB_LIBS=`$PKG_CONFIG --libs "libmaxminddb >= 1.4.3" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -8815,14 +8815,14 @@ else
         _pkg_short_errors_supported=no
 fi
         if test $_pkg_short_errors_supported = yes; then
-	        LIBMAXMINDDB_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libmaxminddb >= 1.6.0" 2>&1`
+	        LIBMAXMINDDB_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libmaxminddb >= 1.4.3" 2>&1`
         else
-	        LIBMAXMINDDB_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libmaxminddb >= 1.6.0" 2>&1`
+	        LIBMAXMINDDB_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libmaxminddb >= 1.4.3" 2>&1`
         fi
 	# Put the nasty error message in config.log where it belongs
 	echo "$LIBMAXMINDDB_PKG_ERRORS" >&5
 
-	as_fn_error $? "Package requirements (libmaxminddb >= 1.6.0) were not met:
+	as_fn_error $? "Package requirements (libmaxminddb >= 1.4.3) were not met:
 
 $LIBMAXMINDDB_PKG_ERRORS