Fix #3732: remove some defects in javalib FileChannel transfer methods

[LeeTibbert]

Fix #3732

javalib java.nio.channels.FileChannel transferFrom and transferTo methods now more closely match
their JDK descriptions. The first now actually transfers data to the destination. The second no longer
moves the position of the source channel.

Both now check their arguments.

The defects described in Issue #3733 remain.

[LeeTibbert]

Lets see what the re-try bunny brings overnight. Right now the "Unix JDK compliance" test
is failing for no reason recorded in the log file. The "Linux multiarch test runtime" looks like
it is going to time out (2+ hours and counting).

Other than than, all is Green, like spring time.