Introduce SNAPPY_ATTRIBUTE_ALWAYS_INLINE.

An internal CL started using ABSL_ATTRIBUTE_ALWAYS_INLINE
from Abseil. This CL introduces equivalent functionality as
SNAPPY_ALWAYS_INLINE.

PiperOrigin-RevId: 306289650

snappy-stubs-internal.h

@@ -37,7 +37,7 @@
 
 #include <cstdint>
 #include <cstring>
-#include <numeric_limits>
+#include <limits>
 #include <string>
 
 #include <assert.h>
@@ -107,6 +107,13 @@
 #define SNAPPY_PREDICT_TRUE(x) x
 #endif
 
+// Inlining hints.
+#ifdef HAVE_ATTRIBUTE_ALWAYS_INLINE
+#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
+#else
+#define SNAPPY_ATTRIBUTE_ALWAYS_INLINE
+#endif
+
 // This is only used for recomputing the tag byte table used during
 // decompression; for simplicity we just remove it from the open-source
 // version (anyone who wants to regenerate it can just do the call