Update Single_crystal.comp

Author: tweber-ill

mcxtrace-comps/samples/Single_crystal.comp

@@ -18,6 +18,7 @@
 * Modified by: EF, PW, 2015: powder and texture mode
 * Modified by: PW, May 2017: Remove statement about being under validation
 * Modified by: PW, June 2017: Doc updates
+* Modified by: T. Weber, October 2017: new focus code
 * Modified by: PW, Feb 2018: GPU edits
 * Modified by: EF, May 2023: (re)port from n to X
 * Modified by: EF, June 2023: can now read CIF files, via cif2hkl