Class with same function name confuses arduino-builder

Correct me if this is an IDE bug.

If a class exists with the same function name of a normal function it will throw an error. Very confusing. just try:

``` cpp
void setup() {}

void loop() {
  rainbow();
}

class CTest {
  public:
    void rainbow() {
      Serial.println("test2");
    }

};

void rainbow() {
  Serial.println("test");
}
```
