Remove use of varargs in SkImageFilter. This is causing a crash in recent

Remove use of varargs in SkImageFilter.  This is causing a crash in recent
builds of clang.  (It was also masking the fact that SkMergeImageFilter was
calling the wrong constructor!)

Committed: https://code.google.com/p/skia/source/detail?r=6029

[Stephen White, 2012-10-22 14:50:43]

PTAL.  No gm's were harmed in the making of this patch.

[robertphillips, 2012-10-22 14:54:02]

LGTM

[reed1, 2012-10-22 17:38:41]

https://codereview.appspot.com/6709066/diff/1/src/core/SkImageFilter.cpp
File src/core/SkImageFilter.cpp (right):

https://codereview.appspot.com/6709066/diff/1/src/core/SkImageFilter.cpp#newc...
src/core/SkImageFilter.cpp:23: 
Seems like a preallocated set of 2 slots would let us avoid these news/deletes
in all cases except merge, which has an arbitrary list.

SkImageFilter** fInputs;
SkImageFilter* fStorageForInputs[2];

if (count <= SK_ARRAY_COUNT(fStorageForInputs)) {
  fInputs = fStorageForInputs;
} else {
  fInputs = new ...
}