Signal code refactoring.

Signal code refactoring.

These patches should not change the current
behavior, although they do fix a few minor bugs which were made
apparent in the process. They are unchanged from my previous post
earlier this month.

    34f5960 _hurd_internal_post_signal: Split into more functions
    420eec9 _hurd_internal_post_signal: Scope variables more restrictively
    1f5accd _hurd_internal_post_signal: Split out inner functions
    1bb0a1d Hurd signals: refactor check_pending_signals
    1764465 Hurd signals: reindent
    28473d2 Hurd signals: make sigsuspend POSIX-conformant.
    26d091a Hurd signals: fix uninitialized value.

Gbp-Pq: Topic hurd-i386
Gbp-Pq: Name tg-hurdsig-fixes.diff