patch 8.2.0660: the search.c file is a bit big

Problem:    The search.c file is a bit big.
Solution:   Split off the text object code to a separate file. (Yegappan
            Lakshmanan, closes #6007)
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index 1830d85..d326174 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -103,6 +103,7 @@
 	tag.c							\
 	term.c							\
 	testing.c						\
+	textobject.c						\
 	textprop.c						\
 	time.c							\
 	ui.c							\