patch 8.2.0156: various typos in source files and tests

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)
diff --git a/src/register.c b/src/register.c
index 24e4b99..6960002 100644
--- a/src/register.c
+++ b/src/register.c
@@ -590,7 +590,7 @@
 	if (y_current->y_array == NULL)
 	    return FAIL;
 
-	// Disallow remaping for ":@r".
+	// Disallow remapping for ":@r".
 	remap = colon ? REMAP_NONE : REMAP_YES;
 
 	// Insert lines into typeahead buffer, from last one to first one.