patch 8.2.0674: some source files are too big

Problem:    Some source files are too big.
Solution:   Move text formatting functions to a new file. (Yegappan
            Lakshmanan, closes #6021)
diff --git a/src/proto.h b/src/proto.h
index d54936c..f8aabc2 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -224,6 +224,7 @@
 # endif
 # include "testing.pro"
 # include "textobject.pro"
+# include "textformat.pro"
 # include "time.pro"
 # include "ui.pro"
 # include "undo.pro"