Fix crash with function declarations with unnamed parameters.

Fixes issue #103.
Previously, we were inadvertently grabbing the function's return type
  for the parameter, rather than the actual parameter type.

decl.cpp

@@ -237,7 +237,7 @@ Declarator::GetType(DeclSpecs *ds) const {
                     sprintf(buf, "__anon_parameter_%d", i);
                     sym = new Symbol(buf, pos);
                     Declarator *declarator = new Declarator(sym, sym->pos);
-                    sym->type = declarator->GetType(ds);
+                    sym->type = declarator->GetType(d->declSpecs);
                     d->declarators.push_back(declarator);
                 }
                 else {

type.cpp

@@ -1833,6 +1833,7 @@ FunctionType::LLVMFunctionType(llvm::LLVMContext *ctx, bool includeMask) const {
     for (unsigned int i = 0; i < argTypes.size(); ++i) {
         if (!argTypes[i])
             return NULL;
+        assert(argTypes[i] != AtomicType::Void);
 
         LLVM_TYPE_CONST llvm::Type *t = argTypes[i]->LLVMType(ctx);
         if (!t)