is_exe: exists check for speed

Author: scivision

+stdlib/is_exe.m

@@ -9,6 +9,8 @@
   use_java (1,1) logical = false
 end
 
+ok = false;
+if ~stdlib.exists(file, use_java), return, end
 
 if use_java
 % about the same time as fileattrib
@@ -20,11 +22,6 @@
 
 else
 
-if ~stdlib.len(p)
-  ok = false;
-  return
-end
-
 [status, v] = fileattrib(p);
 
 ok = status ~= 0 && (v.UserExecute || (~isnan(v.GroupExecute) && v.GroupExecute) || (~isnan(v.OtherExecute) && v.OtherExecute));