Move AudioDecoderIsac* to its own files

Move AudioDecoderIsac* to its own files

Currently, it's sitting in AudioEncoderIsac*'s files, which is less
than obvious. This CL puts the encoder and decoder in separate files
together with the C implementation; CLs are afoot to make it so for
the other built-in codecs as well.

BUG=webrtc:4557
R=henrik.lundin@webrtc.org

Committed: https://crrev.com/740436899825b96e12469c417c0ea82fd8a22edf
Cr-Commit-Position: refs/heads/master@{#10018}

[kwiberg-webrtc, 2015-09-17 06:04:48]

kwiberg@webrtc.org changed reviewers:
+ henrik.lundin@webrtc.org

[kwiberg-webrtc, 2015-09-17 06:08:10]

https://codereview.webrtc.org/1339253003/diff/100001/webrtc/modules/audio_cod...
File webrtc/modules/audio_coding/codecs/isac/fix/source/isac_fix_type.h (right):

https://codereview.webrtc.org/1339253003/diff/100001/webrtc/modules/audio_cod...
webrtc/modules/audio_coding/codecs/isac/fix/source/isac_fix_type.h:119: enum {
kFixSampleRate = 16000 };
I'm sorry to say that I couldn't get this to link without using the enum hack.
If I used a static const int and also defined it in a .cc file, the win compiler
complained about multiple definitions; if I didn't define it in a .cc file, the
linux compiler complained about no definitions.

If anyone has more clever ideas for me to try, I'd prefer to do so in a
follow-up CL so that this one can land already.

[hlundin-webrtc, 2015-09-22 09:21:32]

lgtm

[kwiberg-webrtc, 2015-09-22 13:22:52]

Patchset #8 (id:140001) has been deleted

[kwiberg-webrtc, 2015-09-22 15:24:11]

The CQ bit was checked by kwiberg@webrtc.org

[kwiberg-webrtc, 2015-09-22 15:24:12]

The patchset sent to the CQ was uploaded after l-g-t-m from
henrik.lundin@webrtc.org
Link to the patchset: https://codereview.webrtc.org/1339253003/#ps160001 (title:
"rebase")

[commit-bot: I haz the power, 2015-09-22 15:24:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1339253003/160001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1339253003/160001

[commit-bot: I haz the power, 2015-09-22 15:26:30]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-22 15:26:31]

Try jobs failed on following builders:
  presubmit on tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/presubmit/builds/874)

[kwiberg-webrtc, 2015-09-22 17:31:58]

Committed patchset #8 (id:160001) manually as
740436899825b96e12469c417c0ea82fd8a22edf (presubmit successful).

[commit-bot: I haz the power, 2015-09-22 17:32:02]

Patchset 8 (id:??) landed as
https://crrev.com/740436899825b96e12469c417c0ea82fd8a22edf
Cr-Commit-Position: refs/heads/master@{#10018}