Query the floating point value at key

Property definitions

glesv2 $ GLES :: get_float
	# Query the floating point value at `key`
	private fun get_float(key: Int): Float `{
		GLfloat val;
		glGetFloatv(key, &val);
		return val;
	`}
lib/glesv2/glesv2.nit:815,2--820,3