javadoc warning fixes

[Martin Buchholz]

Here are some easy javadoc warning fixes:

http://cr.openjdk.java.net/~martin/webrevs/openjdk7/nio-javadoc-warnings/

Here are more unfixed warnings in nio-land that I'm not addressing:

../../src/share/classes/java/nio/file/FileRef.java:48: warning - Tag
@see: reference not found: java.io.Inputs
../../src/share/classes/java/nio/file/FileRef.java:48: warning - Tag
@see: reference not found: java.io.Outputs
../../src/share/classes/java/nio/channels/package-info.java:293:
warning - Tag @link: reference not found: java.nio.MappedBigByteBuffer


Martin