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/bit_reader_utils.c

@@ -21,10 +21,13 @@
 #include "src/dsp/cpu.h"
 #include "src/utils/bit_reader_inl_utils.h"
 #include "src/utils/bit_reader_utils.h"
+#include "src/utils/bounds_safety.h"
 #include "src/utils/endian_inl_utils.h"
 #include "src/utils/utils.h"
 #include "src/webp/types.h"
 
+WEBP_ASSUME_UNSAFE_INDEXABLE_ABI
+
 //------------------------------------------------------------------------------
 // VP8BitReader
 
@@ -258,7 +261,7 @@ static void PrintBitTraces(void) {
 void BitTrace(const struct VP8BitReader* const br, const char label[]) {
   int i, pos;
   if (!init_done) {
-    memset(kLabels, 0, sizeof(kLabels));
+    WEBP_UNSAFE_MEMSET(kLabels, 0, sizeof(kLabels));
     atexit(PrintBitTraces);
     buf_start = br->buf;
     init_done = 1;