add clsFilesystemImporter class attribute, alter handling of suffix list
convert suffix importers to funcs rather than instances
remove backwards compat code: Importer.install and 2-tuple get_code()
result values
switch to isinstance() rather than direct type comparisons
removing chaining concept
update ImportManager.install() to take an optional namespace to install
itself in. this will be useful for setting up rexec environments.
minor comment nits
remove use of "os" module (bootstrap issues) and go to the underlying
platform-specific modules
fix problem in _compile() (trapped wrong error on permission issues)
add SysPathImporter and BuiltinImporter
put __file__ into modules imported from the filesystem. [backwards compat]
put __path__ into modules [backwards compat]
oops: it is doing this for all modules, not just packages.
comment and tweak to the PackageArchiveImporter
