Apply "default unsafe" annotation across webputils

Import bounds_safety.h across all of webputils, with one exception being
dsp.h, since it's imported by webputils.h in one place. Also prepend
WEBP_ASSUME_UNSAFE_INDEXABLE_ABI to every webputil file to indicate to
the compiler that every pointer should be treated as __unsafe_indexable.

We also need to replace memcpy/memset/memmove with the unsafe variants
WEBP_UNSAFE_*, as memcpy/memset/memmove require bounded/sized pointers.

With this change, all of libwebputils (and libwebp) should build with
-DWEBP_ENABLE_FBOUNDS_SAFETY=true

Change-Id: Iad87be0455182d534c074ef6dc1a30fa66b74b6c

src/utils/huffman_utils.c

@@ -17,10 +17,13 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "src/utils/bounds_safety.h"
 #include "src/utils/utils.h"
 #include "src/webp/format_constants.h"
 #include "src/webp/types.h"
 
+WEBP_ASSUME_UNSAFE_INDEXABLE_ABI
+
 // Huffman data read via DecodeImageStream is represented in two (red and green)
 // bytes.
 #define MAX_HTREE_GROUPS 0x10000