Polymer: Discard cached sprite planes on texinvalidate

Sprites would stick with their old material on global palette change.
This goes through all prsprites and clobbers their CRCs so that an
alternate skin / tint / highpal can be applied accordingly.

git-svn-id: https://svn.eduke32.com/eduke32@2053 1a8010ca-5511-0410-912e-c29ae57300e0

polymer/eduke32/build/src/polymer.c

@@ -1482,7 +1482,17 @@ void                polymer_invalidatelights(void)
 
 void                polymer_texinvalidate(void)
 {
-    int32_t         i = numsectors-1;
+    int32_t         i;
+
+    i = 0;
+
+    while (i < MAXSPRITES) {
+        if (prsprites[i])
+            prsprites[i]->crc = 0xDEADBEEF;
+        i++;
+    }
+
+    i = numsectors - 1;
 
     if (!numsectors || !prsectors[i])
         return;