platform requirements

[Jonathan Gibbons]

Mark,

In a collection of resolved modules, are there any invariants or 
guarantees about those modules which are identified as platform modules 
by Platform.isPlatformModuleName ?

For example:
-- will there be only one and only one such module in any collection of 
resolved modules
-- will such modules always have no other dependencies?

I'm having to support -Xbootclasspath* options in javac to cope with the 
current jigsaw build, and I'm trying to figure out how tolerant I need 
to be.

-- Jon