patch 8.0.1124: use of MZSCHEME_VER is unclear

Problem:    Use of MZSCHEME_VER is unclear.
Solution:   Add a comment. (Ken Takata)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 33d6dcb..586d36b 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -47,7 +47,9 @@
 #	MzScheme interface:
 #	  MZSCHEME=[Path to MzScheme directory]
 #	  DYNAMIC_MZSCHEME=yes (to load the MzScheme DLLs dynamically)
-#	  MZSCHEME_VER=[version, 205_000, ...] (default is 3m_a0solc (6.6))
+#	  MZSCHEME_VER=[MzScheme version] (default is 3m_a0solc (6.6))
+#	  	Used for the DLL file name. E.g.:
+#	  	C:\Program Files (x86)\Racket\lib\libracket3m_XXXXXX.dll
 #	  MZSCHEME_DEBUG=no
 #
 #	Perl interface: