Add `random()` and `random_seed()`

From the random() reference page:

Generates random numbers. Each time the random() function is called, it returns an unexpected value within the specified range. If only one parameter is passed to the function, it will return a float between zero and the value of the high parameter. For example, random(5) returns values between 0 and 5 (starting at zero, and up to, but not including, 5).

If two parameters are specified, the function will return a float with a value between the two values. For example, random(-5, 10.2) returns values starting at -5 and up to (but not including) 10.2. To convert a floating-point random number to an integer, use the int() function.

From the randomSeed() reference page:

Sets the seed value for random(). By default, random() produces different results each time the program is run. Set the seed parameter to a constant to return the same pseudo-random numbers each time the software is run.

Comienza por las páginas de referencia de random() y randomSeed() enlazadas en el issue y, después, localiza los puntos de entrada correspondientes de la Processing API en libprocessing. Implementa ambas funciones con el comportamiento documentado para uno y dos parámetros, y con una salida determinista al usar una semilla; verifica que la API resultante coincida con esos ejemplos.