SDL_image: configure.ac: Use Autoconf quadrigraphs for character set in AS_CASE

From 79bf1586afe40b840706fb729054dae77e743156 Mon Sep 17 00:00:00 2001
From: Simon McVittie <[EMAIL REDACTED]>
Date: Thu, 5 May 2022 16:15:13 +0100
Subject: [PATCH] configure.ac: Use Autoconf quadrigraphs for character set in
 AS_CASE

The use of square brackets for a character set collides with the use
of square brackets for m4 quote characters, so use the other quoting
mechanism that Autoconf provides, by escaping [ as @<:@ and so on.

Signed-off-by: Simon McVittie <smcv@collabora.com>
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 018d116..2e62602 100644
--- a/configure.ac
+++ b/configure.ac
@@ -19,7 +19,7 @@ AC_SUBST([MICRO_VERSION], MICRO_VERSION_MACRO)
 
 BINARY_AGE=`expr $MINOR_VERSION \* 100 + $MICRO_VERSION`
 AS_CASE(["$MINOR_VERSION"],
-  [*[02468]],
+  [*@<:@02468@:>@],
     dnl Stable branch, 2.6.1 -> libSDL2-2.0.so.0.600.1
     [INTERFACE_AGE="$MICRO_VERSION"],
   [*],