patch 8.0.1646: MS-Windows: executable contains unreferenced functions

Problem:    MS-Windows: executable contains unreferenced functions and data.
Solution:   Add /opt:ref to the compiler command. (Ken Takata)

Author: brammool

src/Make_mvc.mak

@@ -1158,7 +1158,9 @@ LINK_PDB = /PDB:$(VIM).pdb -debug
 # CFLAGS with /Fo$(OUTDIR)/
 CFLAGS_OUTDIR=$(CFLAGS) /Fo$(OUTDIR)/
 
-conflags = /nologo /subsystem:$(SUBSYSTEM)
+# Add /opt:ref to remove unreferenced functions and data even when /DEBUG is
+# added.
+conflags = /nologo /subsystem:$(SUBSYSTEM) /opt:ref
 
 PATHDEF_SRC = $(OUTDIR)\pathdef.c
 

src/version.c

@@ -766,6 +766,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1646,
 /**/
     1645,
 /**/