tree-test: Don't return restricted exit codes

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
base64-test: Remove posibility of returning restricted exit codes

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
dct-test: Remove possibility of returning a restricted exit code

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
fft-test: Remove possibility of returning restricted exit code

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  fft-test: Remove possibility of returning restricted exit code
  dct-test: Remove possibility of returning a restricted exit code
  base64-test: Remove posibility of returning restricted exit codes
  tree-test: Don't return restricted exit codes

Conflicts:
	libavutil/base64.c

See: b2fdf3fc35b6dca8ac7f6d46bd73ea5eb1339193
See: f80ca1cb002c53927fa3edaff5082bfba24d6193
See: cbbd0ac764b43df081898a2c3548a2fee1faca53
See: 5dfdffeb6fe9c43a496a4c1949cf9162474c7418
Merged-by: Michael Niedermayer <michaelni@gmx.at>
doc/utils: document channel layout specification
doc: add a few links to the Channel Layout syntax section
configure: abort if threading without atomics is used

also provide a list of workarounds to the user

Fixes Ticket2363

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