function reFunctionName() {
	return /^\s*function\s*([^(]*)/i;
}
Returns a regular expression to capture everything that is not a space immediately after the `function` keyword and before the first left parenthesis.

@returns {RegExp} regular expression

@example
var RE_FUNCTION_NAME = reFunctionName();

function fname( fcn ) {
    return RE_FUNCTION_NAME.exec( fcn.toString() )[ 1 ];
}

var fn = fname( Math.sqrt );
// returns 'sqrt'

fn = fname( Int8Array );
// returns 'Int8Array'

fn = fname( Object.prototype.toString );
// returns 'toString'

fn = fname( function(){} );
// returns ''