Revert "Suppress icc warnings about unknown attributes"

This reverts r21884.  Apparently people want those warnings.

Originally committed as revision 21954 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -2719,7 +2719,7 @@ if enabled icc; then
     # 144, 167, 556: -Wno-pointer-sign
     # 10006: ignoring unknown option -fno-signed-zeros
     # 10156: ignoring option '-W'; no argument required
-    check_cflags -wd144,167,556,1292,10006,10156
+    check_cflags -wd144,167,556,10006,10156
     # 11030: Warning unknown option --as-needed
     # 10156: ignoring option '-export'; no argument required
     check_ldflags -wd10156,11030