patch 8.2.0997: cannot execute a register containing line continuation

Problem:    Cannot execute a register containing line continuation.
Solution:   Concatenate lines where needed. (Yegappan Lakshmanan,
            closes #6272)
diff --git a/runtime/doc/repeat.txt b/runtime/doc/repeat.txt
index 29cdd73..7b0efdd 100644
--- a/runtime/doc/repeat.txt
+++ b/runtime/doc/repeat.txt
@@ -163,6 +163,11 @@
 			result of evaluating the expression is executed as an
 			Ex command.
 			Mappings are not recognized in these commands.
+			When the |line-continuation| character (\) is present
+			at the beginning of a line in a linewise register,
+			then it is combined with the previous line. This is
+			useful for yanking and executing parts of a Vim
+			script.
 			Future: Will execute the register for each line in the
 			address range.