Allow capturing non-public functions as values.

sourcepawn/compiler/tests/fail-callback-returns-array.sp

@@ -0,0 +1,16 @@
+String:MyFunction()
+{
+  new String:egg[10] = "egg";
+  return egg;
+}
+
+public crab()
+{
+  new String:egg[10];
+  egg = MyFunction();
+}
+
+public Function:main()
+{
+  return MyFunction;
+}

sourcepawn/compiler/tests/fail-callback-returns-array.txt

@@ -0,0 +1 @@
+(15) : error 182: functions that return arrays cannot be used as callbacks

sourcepawn/compiler/tests/fail-newdecls.txt

@@ -2,4 +2,4 @@
 (2) : error 141: natives, forwards, and public functions cannot return arrays
 (3) : error 143: new-style declarations should not have "new"
 (5) : error 121: cannot specify array dimensions on both type and name
-(11) : error 025: function heading differs from prototype
+(11) : error 180: function return type differs from prototype. expected 'void', but got 'int'