Replace errant tabs with spaces in causes.h.

(closes issue ASTERISK-20826)
Reported by: snuffy
Patches:
	notabs.dif uploaded by snuffy (license 5024)


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@378733 f38db490-d61c-443f-a65b-d21fe96a405b