Add invalid tests

syntax/basic_type_as_constructor.invalid.mj

+class BasicTypeAsConstructor {
+    new int();
+}

syntax/forgotten_assignment.invalid.mj

+class ClassicStudentProblems {
+    public int and(Then did) throws not {
+        return to=klass=the=next=;
+    }
+}

syntax/pre_incr_vs_pre_decr.invalid.mj

+class PreDecrementIsNotWhatItSeems {
+    --thisIsTotallyFine - !!!++butThisIsNot;
+}

syntax/primary_expr_as_field_access.invalid.mj

+class PrimaryExprAsFieldAccess {
+    1234.null;
+}

syntax/throwing_with_keywords.invalid.mj

+class ThrowingWithKeywordsInAnIdentHouse {
+    public static void main(String[] _what_) throws int {
+
+    }
+    /* Writing in languages where NullPointerExceptions are a thing, pfff */
+    public void again(Questionmark questionmark) throws null {
+
+    }
+}