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)

src/memline.c

@@ -111,7 +111,7 @@ struct data_block
     unsigned	db_txt_end;	// byte just after data block
     linenr_T	db_line_count;	// number of lines in this block
     unsigned	db_index[1];	// index for start of line (actually bigger)
-				// followed by empty space upto db_txt_start
+				// followed by empty space up to db_txt_start
 				// followed by the text in the lines until
 				// end of page
 };