Created utility function to extract extension from filename, fixed tests

programs/util.h

@@ -135,6 +135,8 @@ int UTIL_getFileStat(const char* infilename, stat_t* statbuf);
 int UTIL_isSameFile(const char* file1, const char* file2);
 int UTIL_compareStr(const void *p1, const void *p2);
 int UTIL_isCompressedFile(const char* infilename, const char *extensionList[]);
+const char* UTIL_getFileExtension(const char* infilename);
+
 U32 UTIL_isFIFO(const char* infilename);
 U32 UTIL_isLink(const char* infilename);
 #define UTIL_FILESIZE_UNKNOWN  ((U64)(-1))