Merged from trunk 10997:10999

   Merged from trunk 10997:10999

   | 10998   | Fix SubProcess._poll to handle a missing pid gracefully.     |
   | zmedico |                                                              |

   | 10999   | * Unify the scheduler's "build" and "extract" queues into a  |
   | zmedico | single "jobs" queue. * Add support for logging fetches to    |
   |         | /var/log/emerge-fetch.log when --jobs is enabled. Previously |
   |         | this log was only used for the parallel-fetch feature but    |
   |         | now it's also used for --jobs. The scheduler's "prefetch"    |
   |         | queue has been renamed to "fetch" since it's not exclusively |
   |         | used for parallel-fetch anymore. * Pass the "background"     |
   |         | parameter from Binpkg in to the BinpkgFetcher instance, to   |
   |         | send output to emerge-fetch.log instead of stdout.           |

svn path=/main/branches/prefix/; revision=11001