patch 8.2.0489: Vim9: memory leaks

Problem:    Vim9: memory leaks.
Solution:   Free memory in the right place.  Add hints for using asan.
diff --git a/src/Makefile b/src/Makefile
index 690ac3f..221b4f0 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -691,9 +691,12 @@
 
 
 # Uncomment one of the next two lines to compile Vim with the
-# address sanitizer or with the undefined sanitizer.  Works with gcc and
+# address sanitizer (asan) or with the undefined sanitizer.  Works with gcc and
 # clang.  May make Vim twice as slow.  Errors reported on stderr.
 # More at: https://code.google.com/p/address-sanitizer/
+# Useful environment variables:
+# $ export ASAN_OPTIONS="print_stacktrace=1 log_path=asan"
+# $ export LSAN_OPTIONS="suppressions=$cwd/testdir/lsan-suppress.txt"
 #SANITIZER_CFLAGS = -g -O0 -fsanitize=address -fno-omit-frame-pointer
 #SANITIZER_CFLAGS = -g -O0 -fsanitize=undefined -fno-omit-frame-pointer
 SANITIZER_LIBS = $(SANITIZER_CFLAGS)