glx: DoQueryContext(): use fixed size array instead of variable length

Our array here really is fixed, but it's size is determined by a variable
(that's assigned a fix values), unncessarily making it a VLA (even making
it const doesn't change that), so giving false alarms when compiling w/
-Wvla or -Werror=vla.

Replacing the variable by #define trivially fixes this.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1665>
(cherry picked from commit 0a7763bfce)

glx/glxcmds.c

@@ -1652,13 +1652,14 @@ __glXDisp_SwapBuffers(__GLXclientState * cl, GLbyte * pc)
     return Success;
 }
 
+#define GLX_QUERY_NPROPS 5
+
 static int
 DoQueryContext(__GLXclientState * cl, GLXContextID gcId)
 {
     ClientPtr client = cl->client;
     __GLXcontext *ctx;
-    int nProps = 5;
-    int sendBuf[nProps * 2];
+    int sendBuf[GLX_QUERY_NPROPS * 2];
     int nReplyBytes;
     int err;
 
@@ -1668,8 +1669,8 @@ DoQueryContext(__GLXclientState * cl, GLXContextID gcId)
     xGLXQueryContextInfoEXTReply reply = {
         .type = X_Reply,
         .sequenceNumber = client->sequence,
-        .length = nProps << 1,
-        .n = nProps
+        .length = GLX_QUERY_NPROPS  << 1,
+        .n = GLX_QUERY_NPROPS,
     };
 
     nReplyBytes = reply.length << 2;
@@ -1704,6 +1705,8 @@ DoQueryContext(__GLXclientState * cl, GLXContextID gcId)
     return Success;
 }
 
+#undef GLX_QUERY_NPROPS
+
 int
 __glXDisp_QueryContextInfoEXT(__GLXclientState * cl, GLbyte * pc)
 {