Use task_t, thread_t, and exception_handler_t uniformly

Use more-specific typedefs for send rights to task, thread, and
exception handler ports.

task_t, thread_t, and exception_handler_t are typedefs for mach_port_t.
They are more descriptive than mach_port_t, and are already in use in
exc_server_variants.

TEST=util_test
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/4d35ffa80ebafdcdec5b580323a1005b182d2ec9

[Mark Mentovai, 2014-09-18 16:16:12]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Mark Mentovai, 2014-09-18 16:16:13]

https://codereview.chromium.org/577293002/diff/1/util/mach/mach_message_serve...
File util/mach/mach_message_server.cc (left):

https://codereview.chromium.org/577293002/diff/1/util/mach/mach_message_serve...
util/mach/mach_message_server.cc:136: mach_port_t self = mach_task_self();
This was the only place in bpoop where mach_task_self() was cached in a local
variable.

Since we know how mach_task_self() actually works, it’s pointless to cache it in
a local. In all modern code, I just use it inline wherever I need it.

[Robert Sesek, 2014-09-18 16:44:31]

LGTM

[Mark Mentovai, 2014-09-18 17:53:48]

Committed patchset #1 (id:1) manually as 4d35ffa (presubmit successful).