function logf( x, b ) {
	return addon( x, b );
}
Computes the base `b` logarithm of a single-precision floating-point number.

@private
@param {number} x - input value
@param {number} b - input value
@returns {number} function value

@example
var v = logf( 100.0, 10.0 );
// returns 2.0

@example
var v = logf( 16.0, 2.0 );
// returns 4.0

@example
var v = logf( -4.0, 1.0 );
// returns NaN