- rename CompManager.cmLoadModule to cmLoadModules and make it take
  a DynFlags argument to be consistent with the rest of the
  CompManager interface.

- split cmLoadModule into two parts: cmDepAnal which takes a list of
  filenames and returns a ModuleGraph, and cmLoadModules which takes
  the ModuleGraph and does the rest.  This lets the consumer know
  whether the dependency analysis step fails before unloading any
  existing modules - i.e. if you :reload and a module is missing, you
  don't lose the modules that are already loaded (bug reported by
  MIchael Weber some time ago).