Add some tests.

sourcepawn/compiler/tests/fail-ctor-bad-return-type.sp

@@ -0,0 +1,13 @@
+native Float:CreateHandle(count);
+native CloseHandle(Handle:handle);
+
+methodmap Handle {
+	public Handle = CreateHandle;
+	public Close = CloseHandle;
+};
+
+public main() {
+	new Handle:handle = Handle(3);
+	handle.Close();
+}
+

sourcepawn/compiler/tests/fail-ctor-bad-return-type.txt

@@ -0,0 +1 @@
+constructor function must return tag Handle

sourcepawn/compiler/tests/fail-duplicate-methods.sp

@@ -0,0 +1,8 @@
+native X:Crab();
+methodmap X {
+	public X = Crab;
+	public X = Crab;
+}
+
+public main() {
+}

sourcepawn/compiler/tests/fail-duplicate-methods.txt

@@ -0,0 +1 @@
+X was already defined on this methodmap