patch 8.2.0847: typval related code is spread out

Problem:    Typval related code is spread out.
Solution:   Move code to new typval.c file. (Yegappan Lakshmanan, closes #6093)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index 43414e7..4efc1d6 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -107,6 +107,7 @@
 	textobject.c						\
 	textprop.c						\
 	time.c							\
+	typval.c						\
 	ui.c							\
 	undo.c							\
 	usercmd.c						\