doc: create alias man pages for large count routines

We list the large count routines in the same man page of their normal
count routines, but the entries are missing. This commit creates the
alias man pages for them.

maint/alias_mancnst

@@ -25,3 +25,15 @@ while (<In>) {
     }
 }
 close In;
+
+# large count routines
+open In, "grep '^int MPI\\w*_c\\>' man/man3/*.3 |" or die "Failed to grep for large count man pages\n";
+while (<In>) {
+    # e.g. [man/man3/MPI_Recv.3:int MPI_Recv_c(void *buf, MPI_Count count, MPI_Datatype datatype, int source,] 
+    if (/^man\/man3\/(MPI\w+)\.3:int (MPI\w+_c)\(/) {
+        open Out, "> man/man3/$2.3" or die "Can't create man/man3/$2.3\n";
+        print Out ".so man3/$1.3\n";
+        close Out;
+    }
+}
+close In;