wp-login form user_email

[scottconnerly]

The registerform in wp-login should utilize the new HTML5 field type of "email" for the user_email input.

Use case is for mobile devices that display contextual keyboards based on the desired input.
Eg: ​http://developer.apple.com/library/safari/#codinghowtos/Mobile/UserExperience/_index.html

Related: #17863

In [18763]:

Use input type=email on wp-login registration. props scottconnerly, fixes #18761.

wp-signup.php is too much of a mess for me to want to change that here.