Migrate to standard integral types.

The following changes are done via find/replace.
* int8 -> int8_t
* int16 -> int16_t
* int32 -> int32_t
* int64 -> int64_t

The aliases were removed from snappy-stubs-public.h.

PiperOrigin-RevId: 306141557

snappy-stubs-internal.cc

@@ -33,7 +33,7 @@
 
 namespace snappy {
 
-void Varint::Append32(std::string* s, uint32 value) {
+void Varint::Append32(std::string* s, uint32_t value) {
   char buf[Varint::kMax32];
   const char* p = Varint::Encode32(buf, value);
   s->append(buf, p - buf);