Minor usage change - one comma!

fslchpixdim

@@ -9,7 +9,7 @@
 #   SHCOPYRIGHT
 
 if [ $# -lt 4 ] ; then
-  echo "Usage: $0 <hdrfile> <xdim> <ydim> <zdim> [tdim]      (in mm or seconds for tdim)"
+  echo "Usage: $0 <hdrfile> <xdim> <ydim> <zdim> [tdim]      (in mm, or seconds for tdim)"
   echo "WARNING: This will set default s/q-form values for NIFTI files"
   exit 1;
 fi