Renamed RealtimeAnalyserNode to AnalyserNode

+ Added a RealtimeAnalyserNode constructor (that extends AnalyserNode)
for backwards compatibility. The RealtimeAnalyserNode constructor has
been flagged as deprecated.
Merge pull request #460 from retromodular/audio-externs-update

Renamed RealtimeAnalyserNode (w3c_audio)
Accept JSDoc for let and const declarations
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69642994
Transpile let/const declarations captured by loop closures
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69657023
Class side inheritance by explicitly copying inherited members.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69661887