patch 9.1.1252: typos in code and docs related to 'diffopt' "inline:"

Problem:  Typos in code and docs related to 'diffopt' "inline:".
          (after v9.1.1243)
Solution: Fix typos and slightly improve the docs.
          (zeertzjq)

closes: #16997

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/structs.h b/src/structs.h
index 33c26dc..0baf543 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3606,7 +3606,7 @@
 struct diffline_change_S
 {
     colnr_T	dc_start[DB_COUNT];	// byte offset of start of range in the line
-    colnr_T	dc_end[DB_COUNT];	// 1 paste byte offset of end of range in line
+    colnr_T	dc_end[DB_COUNT];	// 1 past byte offset of end of range in line
     int		dc_start_lnum_off[DB_COUNT];	// starting line offset
     int		dc_end_lnum_off[DB_COUNT];	// end line offset
 };