RFR 8015402 -- lambda metafactory simplifications

[Brian Goetz]

The following webrev describes changes to the lambda metafactory enabled 
by the compiler generating bridge methods in interfaces, and therefore 
the metafactory need not try and guess which other methods should be 
bridged to the main SAM method.  The compiler can optionally generate a 
specific list of alternate signatures to be bridged.

   http://cr.openjdk.java.net/~briangoetz/JDK-8015402