ZAM fixes for assignments involving "any" record fields

testing/btest/Baseline/opt.regress-any/output

@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+[a=123, b=[abc]]
+[a=123, b=1]

testing/btest/opt/regress-any.zeek

@@ -0,0 +1,16 @@
+# @TEST-DOC: Regression test for reassigning an "any" field
+# @TEST-EXEC: zeek -b -O ZAM %INPUT >output
+# @TEST-EXEC: btest-diff output
+
+type X: record {
+	a: string;
+	b: any;
+};
+
+event zeek_init()
+	{
+	local x = X($a="123", $b=vector("abc"));
+	print x;
+	x$b = 1;
+	print x;
+	}