better doxygen doc for CPC loaders

src/cpc_scr_simple_loader.h

@@ -1,7 +1,10 @@
 /* vim:expandtab:ts=2 sw=2:
  */
 /**
- * author : unknown
+ * CPC Z80 code to be put in a "gap" of an image (at address &C7D0).
+ * Sets the screen mode (from &D7D0), then sets the border and the palette
+ * (Firmware colors) at &D7D1
+ * @author unknown
  */
 static const unsigned char cpc_scr_simple_loader[] = {
  0x3a, 0xd0, 0xd7,  // C7D0 LD A,(D7D0)

src/impdraw_loader.h

@@ -2,9 +2,9 @@
  */
 /**
  * Amstrad CPC Loader for overscan picture.
- * Locomotive BASIC + Z80 Code
- * (c) Ast/iMP4CT
- * https://amstradplus.forumforever.com/t462-iMPdraw-v2-0.htm?start=45
+ * Locomotive BASIC + Z80 Code.
+ * @author Ast/iMP4CT
+ * @see https://amstradplus.forumforever.com/t462-iMPdraw-v2-0.htm?start=45
  */
 static const unsigned char impdraw_loader[] = {
   0x0e, 0x00, 0x0a, 0x00, 0x01, 0xc0, 0x20, 0x69, // starts at &0170