indeo3: add parens around some macro arguments

Without these, the expansion contains things like --1 with
some compilers resulting in build errors.

Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/indeo3data.h

@@ -247,8 +247,8 @@
  * Expand a pair of delta values (a,b)
  * into two/four delta entries.
  */
-#define E2(a, b) PD(a, b), PD(-a, -b)
-#define E4(a, b) PD(a, b), PD(-a, -b), PD(b, a), PD(-b, -a)
+#define E2(a, b) PD(a, b), PD(-(a), -(b))
+#define E4(a, b) PD(a, b), PD(-(a), -(b)), PD(b, a), PD(-(b), -(a))
 
 /*
  * VQ tables for 4x4 block modes.