patch 8.2.0443: clipboard code is spread out

Problem:    Clipboard code is spread out.
Solution:   Move clipboard code to its own file. (Yegappan Lakshmanan,
            closes #5827)
diff --git a/src/Make_vms.mms b/src/Make_vms.mms
index 32857de..ea6a8d7 100644
--- a/src/Make_vms.mms
+++ b/src/Make_vms.mms
@@ -306,6 +306,7 @@
 	change.c \
 	charset.c \
 	cindent.c \
+	clipboard.c \
 	cmdexpand.c \
 	cmdhist.c \
 	crypt.c \
@@ -412,6 +413,7 @@
 	change.obj \
 	charset.obj \
 	cindent.obj \
+	clipboard.obj \
 	cmdexpand.obj \
 	cmdhist.obj \
 	crypt.obj \
@@ -700,6 +702,10 @@
  ascii.h keymap.h term.h macros.h structs.h regexp.h \
  gui.h beval.h [.proto]gui_beval.pro option.h ex_cmds.h proto.h \
  globals.h
+clipboard.obj : clipboard.c vim.h [.auto]config.h feature.h os_unix.h \
+ ascii.h keymap.h term.h macros.h structs.h regexp.h \
+ gui.h beval.h [.proto]gui_beval.pro option.h ex_cmds.h proto.h \
+ globals.h
 cmdexpand.obj : cmdexpand.c vim.h [.auto]config.h feature.h os_unix.h \
  ascii.h keymap.h term.h macros.h structs.h regexp.h \
  gui.h beval.h [.proto]gui_beval.pro option.h ex_cmds.h proto.h \