RFR: 8282444: Module finder incorrectly assumes default file system path-separator character

[Chris Hegarty]

The module finder implementation incorrectly uses the path-separator
character from the default file system, when mapping the relative path
of an entry in an exploded module to a package name. This causes
problems on Windows [*] when using a module finder with a custom file
system that has a path-separator character that differs from that of the
default file system, e.g. the zip file system (which uses '/',
rather than '\' ).

Rather than adding a new test for this, I deciced to just modify an
existing one. The existing test exercises the module finder with a
custom file system, but does so with modules have trivial single-level
packages names. I just expanded the module to have a subpackage. This
is sufficient to reproduce the bug, and verify the fix.

[*]

java.lang.module.FindException: Error reading module: /m2
        at java.base/jdk.internal.module.ModulePath.readModule(ModulePath.java:350)
        at java.base/jdk.internal.module.ModulePath.scanDirectory(ModulePath.java:284)
        at java.base/jdk.internal.module.ModulePath.scan(ModulePath.java:232)
        at java.base/jdk.internal.module.ModulePath.scanNextEntry(ModulePath.java:190)
        at java.base/jdk.internal.module.ModulePath.findAll(ModulePath.java:166)
        at ModulesInCustomFileSystem.listAllModules(ModulesInCustomFileSystem.java:108)
        at ModulesInCustomFileSystem.testZipFileSystem(ModulesInCustomFileSystem.java:97)
        at ModulesInCustomFileSystem.testExplodedModulesInZipFileSystem(ModulesInCustomFileSystem.java:68)
        at ...
Caused by: java.lang.module.InvalidModuleDescriptorException: Package q.r not found in module
        at java.base/jdk.internal.module.ModuleInfo.invalidModuleDescriptor(ModuleInfo.java:1212)
        at java.base/jdk.internal.module.ModuleInfo.doRead(ModuleInfo.java:330)
        at java.base/jdk.internal.module.ModuleInfo.read(ModuleInfo.java:129)
        at java.base/jdk.internal.module.ModulePath.readExplodedModule(ModulePath.java:689)
        at java.base/jdk.internal.module.ModulePath.readModule(ModulePath.java:320)
        ... 36 more

-------------

Commit messages:
 - fix file separator in module finder with custom fs

Changes: https://git.openjdk.java.net/jdk/pull/7632/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7632&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282444
  Stats: 7 lines in 4 files changed: 1 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7632.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7632/head:pull/7632

PR: https://git.openjdk.java.net/jdk/pull/7632