Add support for "don't care" in the result file.
Add support for "don't care" in the result file.

The result file (with the file extension .res) stores a numeric
aom_codec_err_t value on each line. Since all aom_codec_err_t values are
0 (AOM_CODEC_OK) or positive, we can use the value -1 to indicate a
wildcard, "don't care" value. This special value is considered to match
any decode result.

Use case: Depeding on whether libaom is compiled with
-DAOM_MAX_ALLOCABLE_MEMORY=1073741824, the decoding of an invalid frame
may fail with AOM_CODEC_MEM_ERROR or AOM_CODEC_CORRUPT_FRAME. We need a
way to match either decode result value.

Change-Id: Ia3e3d99a713a309cf07832bfe511de5d2715f0bb

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom