Add forgotten leading underscore to _PROTECTED_WRITE.

Thanks to Joakim for noticing this.


git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2404 1084037a-409f-4a99-8160-1a4b3577d4c1
Merge remote-tracking branch 'upstream/master' into avr-libc-embecosm-mainline

Conflicts (resolved):
	avr-libc/ChangeLog