Cursor blinking should respect NSTextInsertionPointBlinkPeriod

To reproduce:

1. In terminal enter:
    defaults write -g NSTextInsertionPointBlinkPeriod -int 100000000
    defaults write -g CursorBlink -string 0
2. Re-login?, restart browser 
3. Open any webpage with input/textarea fileds and try to type some text
4. See if cursor is blinking after you stop typing

Cursor should stop blinking in text fields, but it doesn't.

Affects Safari, Chrome and webviews inside apps.

Yes, RenderTheme hardcodes the interval to 0.5.

>    defaults write -g NSTextInsertionPointBlinkPeriod -int 100000000

This is not a perfect way to disable blinking. The value is in milliseconds, and equals ~27 hours. So after this period, the cursor will disappear.

>    defaults write -g CursorBlink -string 0

This is a preference of Terminal.app that should have no effect on other applications.

For Apple employees, see also <rdar://problem/13196044>.