[bug 66535] X-PHP-Originating-Script adds newline if no custom headers are given

A newline is added to the mail headers when mail.add_x_header is used and no other headers are passed to mail().

The scenario in which custom headers are used was already fixed in #48620, back in 2009.
Fixed test case title
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  Fixed test case title
  [bug 66535] X-PHP-Originating-Script adds newline if no custom headers are given