patch 8.2.3824: no ASAN support for MSVC

Problem:    No ASAN support for MSVC.
Solution:   Add ASAN support and fix a coupld of uncovered problems. (Yegappan
            Lakshmanan, closes #9357)
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 6be13fb..2417d77 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -147,6 +147,8 @@
 #
 #	Static Code Analysis: ANALYZE=yes (works with VS2012 or later)
 #
+#	Address Sanitizer: ASAN=yes (works with VS2019 or later)
+#
 # You can combine any of these interfaces
 #
 # Example: To build the non-debug, GUI version with Perl interface:
@@ -662,6 +664,12 @@
 CFLAGS = $(CFLAGS) /analyze
 !endif
 
+# Address Sanitizer (ASAN) generally available starting with VS2019 version
+# 16.9
+!if ("$(ASAN)" == "yes") && ($(MSVC_MAJOR) >= 14)
+CFLAGS = $(CFLAGS) /fsanitize=address
+!endif
+
 !ifdef NODEBUG
 VIM = vim
 ! if "$(OPTIMIZE)" == "SPACE"