Update FontConfig valgrind suppressions.

FcPattern uses 'intptr_t elts_offsets' instead of 'FcPatternEltPtr elts'
to reference its elements. Therefore, valgrind suspects possible leaks
on all values, elements, and element lists in FontConfig.

BUG=skia:2879
R=djsollen@google.com, mtklein@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/518903002

tools/valgrind.supp

@@ -96,9 +96,19 @@
     font_config_bug_2
     Memcheck:Leak
     fun:*alloc
-    fun:FcPatternObjectInsertElt
+    ...
     fun:Fc*Add*
 }
+{
+    #Same root cause as font_config_bug_2.
+    #The 'leak' here is a copy of rule values, as opposed to new values.
+    font_config_bug_3
+    Memcheck:Leak
+    fun:*alloc
+    fun:FcConfigValues
+    fun:FcConfigSubstituteWithPat
+    fun:FcFontRenderPrepare
+}
 {
     zlib_bug_1
     Memcheck:Cond