[youtube] add support for format 298(720p60) and 299(1080p60)

[sdsucks]

E:>youtube-dl -v -w -c -i -F TNMiA4ut9zA
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['-v', '-w', '-c', '-i', '-F', 'TNMiA4ut9zA']
[debug] Encodings: locale cp949, fs mbcs, out cp949, pref cp949
[debug] youtube-dl version 2014.10.27
[debug] Python version 2.7.8 - Windows-7-6.1.7601-SP1
[debug] exe versions: ffmpeg N-67250-
[debug] Proxy map: {}
[youtube] Confirming age
[youtube] TNMiA4ut9zA: Downloading webpage
[youtube] TNMiA4ut9zA: Downloading video info webpage
[youtube] TNMiA4ut9zA: Extracting video information
[youtube] TNMiA4ut9zA: Downloading DASH manifest
[info] Available formats for TNMiA4ut9zA:
format code extension resolution note
139 m4a audio only DASH audio 60k , audio@ 48k (22050Hz), 1.21MiB (worst)
140 m4a audio only DASH audio 166k , audio@128k (44100Hz), 3.22MiB
141 m4a audio only DASH audio 306k , audio@256k (44100Hz), 6.39MiB
160 mp4 256x144 DASH video 112k , video only, 2.73MiB
133 mp4 426x240 DASH video 247k , video only, 6.13MiB
134 mp4 640x360 DASH video 611k , video only, 14.96MiB
135 mp4 854x480 DASH video 1112k , video only, 27.41MiB
136 mp4 1280x720 DASH video 2220k , video only, 54.85MiB
137 mp4 1920x1080 DASH video 4149k , video only, 103.50MiB
298 unknown_video?x1280 3333k , 82.11MiB
299 unknown_video?x1920 5564k , 137.66MiB
17 3gp 176x144
36 3gp 320x240
5 flv 400x240
18 mp4 640x360
22 mp4 1280x720 (best)