new Create account contributors icon

This is more gender-neutral and better relates to the background image
glyph-people-large.png behind the new Login form's link to create an
account. It's only 45px high not 75 but lays out OK in Firefox 21,
Chromium 25, and IE7.

Change-Id: I2a4aba718a15b5f2ee9129536584304a461874dd
Merge "new Create account contributors icon"