Batch compiler is inconsistent about separators for package names

[stephan-herrmann]

addresses issue #1458:

This just illustrates a medium, incomplete cleanup towards more consistency.

[stephan-herrmann]

I tried to identify a few "sinks" that seem to "need" File.separatorChar:

• use of java.io.File etc.
• creation of ClassFileReader
• access to certain cache fields, like ClasspathDirectory#packageSecondaryTypes and #directoryCache
• also field ClasspathLocation#path seems to be intended for use with File.separatorChar

In all other cases unconditionally using / looks more straight forward, as it conforms to

• binary names in byte code
• paths inside archives incl. jrt

[stephan-herrmann]

I'll let it rest until I hear from others, in particular on the (non-)necessity of using File.separatorChar at all.