Improved error messages for foo(void), foo(int!) declarations.

test/test_suite/abi/darwinx64_2.c3t

@@ -6,7 +6,7 @@ struct St12
 {
     int a @align(16);
 }
-fn St12 f12_0(void) { while (1) {}; unreachable(); }
+fn St12 f12_0() { while (1) {}; unreachable(); }
 fn void f12_1(St12 a0) {}
 
 struct St13_0 { long[3] f0; }

test/test_suite/clang/2002-04.c3t

@@ -39,7 +39,7 @@ struct St {
 
 extern fn St func_returning_struct();
 
-fn void loop(void) {
+fn void loop() {
   func_returning_struct();
 }
 

test/test_suite/functions/failable_param.c3

@@ -0,0 +1,3 @@
+module test;
+
+fn void test4(void!); // #error: Parameters may not be failable.

test/test_suite/functions/void_params.c3

@@ -0,0 +1,2 @@
+fn void test(int, void) {} // #error: Parameters may not be of type 'void'.
+fn void test3(void); // #error: C-style 'foo(void)' style argument declarations are not valid

test/test_suite2/abi/darwinx64_2.c3t

@@ -6,7 +6,7 @@ struct St12
 {
     int a @align(16);
 }
-fn St12 f12_0(void) { while (1) {}; unreachable(); }
+fn St12 f12_0() { while (1) {}; unreachable(); }
 fn void f12_1(St12 a0) {}
 
 struct St13_0 { long[3] f0; }

test/test_suite2/clang/2002-04.c3t

@@ -39,7 +39,7 @@ struct St {
 
 extern fn St func_returning_struct();
 
-fn void loop(void) {
+fn void loop() {
   func_returning_struct();
 }
 

test/test_suite2/functions/failable_param.c3

@@ -0,0 +1,3 @@
+module test;
+
+fn void test4(void!); // #error: Parameters may not be failable.

test/test_suite2/functions/void_params.c3

@@ -0,0 +1,2 @@
+fn void test(int, void) {} // #error: Parameters may not be of type 'void'.
+fn void test3(void); // #error: C-style 'foo(void)' style argument declarations are not valid