added minimum for decoder buffer

also : introduced macro BOUNDED()

lib/common/zstd_internal.h

@@ -57,6 +57,7 @@ extern "C" {
 #undef MAX
 #define MIN(a,b) ((a)<(b) ? (a) : (b))
 #define MAX(a,b) ((a)>(b) ? (a) : (b))
+#define BOUNDED(min,val,max) (MAX(min,MIN(val,max)))
 
 
 /*-*************************************