http: Check the auth string contents and not only the pointer

This makes sure we don't send the Except: 100-continue header
if no authentication credentials have been provided.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  http: Check the auth string contents and not only the pointer

Conflicts:
	libavformat/http.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/jpeg2000dec: fix context consistency with too large lowres

Fixes out of array accesses
Fixes Ticket2898

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>