vpxdec: Relocate WebM input support.

- Move it to webmdec.c and webmdec.h.
- Also, tidy up obvious style nits in the vicinity of code I was
  already touching.

Change-Id: Ie2898d06e73c1e9030d9c8d465b73ee7edc3c02a

tools_common.h

diff --git a/tools_common.h b/tools_common.h
index 353f90a..7500523 100644
--- a/tools_common.h
+++ b/tools_common.h
@@ -92,11 +92,11 @@
   off_t length;
   struct FileTypeDetectionBuffer detect;
   enum VideoFileType file_type;
-  unsigned int width;
-  unsigned int height;
+  uint32_t width;
+  uint32_t height;
   int use_i420;
   int only_i420;
-  unsigned int fourcc;
+  uint32_t fourcc;
   struct VpxRational framerate;
 #if CONFIG_ENCODERS
   y4m_input y4m;