config.c: do not pre-check if (un)compresscmd is executable

The execlp/execvp calls that execute them search for executables
in $PATH, which access(..., X_OK) does not support.  This commit
makes it possible to specify the (un)compress commands by their
base name only in case they are available in $PATH.

Closes #122

config.c

@@ -1433,13 +1433,6 @@ static int readConfigFile(const char *configFile, struct logInfo *defConfig)
 						RAISE_ERROR();
 					}
-					if (access(newlog->compress_prog, X_OK)) {
-						message(MESS_ERROR,
-							"%s:%d compression program %s is not an executable file\n",
-							configFile, lineNum, newlog->compress_prog);
-						RAISE_ERROR();
-					}
-
 					message(MESS_DEBUG, "compress_prog is now %s\n",
 						newlog->compress_prog);
@@ -1465,13 +1458,6 @@ static int readConfigFile(const char *configFile, struct logInfo *defConfig)
 						RAISE_ERROR();
 					}
-					if (access(newlog->uncompress_prog, X_OK)) {
-						message(MESS_ERROR,
-							"%s:%d uncompression program %s is not an executable file\n",
-							configFile, lineNum, newlog->uncompress_prog);
-						RAISE_ERROR();
-					}
-
 					message(MESS_DEBUG, "uncompress_prog is now %s\n",
 						newlog->uncompress_prog);