Clean up MEX example code. * myfeval.c: Use mxIsChar rather than deprecated mxIsString. * mypow2.c: Validate that input is a double matrix. * myprop.c: Use space after '!' operator to conform to Octave conventions. * myset.c: Use mexPutVariable instead of missing mxSetName and deprecated mexPutArray. Find existing variable EITHER in global workspace OR in caller workspace. Don't check both. * mystruct.c: Clarify input validation message.

--- a/examples/code/mystruct.c
+++ b/examples/code/mystruct.c
@@ -10,7 +10,7 @@
   const char *keys[] = { "this", "that" };
 
   if (nrhs != 1 || ! mxIsStruct (prhs[0]))
-    mexErrMsgTxt ("expects struct");
+    mexErrMsgTxt ("ARG1 must be a struct");
 
   for (i = 0; i < mxGetNumberOfFields (prhs[0]); i++)
     for (j = 0; j < mxGetNumberOfElements (prhs[0]); j++)