Remove $loopback-address, $local-host, and $local-host-name
Add function local-host-name

These were no constant values, but variables. Additionally, they
confused me multiple times, since initialized by start-sockets(),
which used gethostname and passed that to gethostbyname - which
does not work on poorly configured computers which do not have DNS
or /etc/hosts setup properly.

This also updates all clients in the opendylan repository and updates
the documentation to reflect the changes.
add release note item for network library change
Merge pull request #498 from hannesm/reduce-network-confusion

Remove $loopback-address, $local-host, and $local-host-name
[rt] Fix multiply defined symbols.

We implement some stuff in boehm-collector and now use it from
the C run-time.
[rt] Stub out symbols for the C run-time.
debugger-manager: Properly handle 0b11 tag values

Tag value 0b11 is currently used to represent <unicode-character> instances
(cf. sources/dylan/boot.dylan). This tag value needs to be recognized
by the debugger.

* sources/runtime-manager/debugger-manager/dfmc-accessors.dylan
  ($dylan-tag-unichar): New constant.
  (dylan-object?): Handle the $dylan-tag-unichar case.

* sources/runtime-manager/debugger-manager/queries.dylan
  (dylan-object-size): Handle the $dylan-tag-unichar case.

* sources/runtime-manager/debugger-manager/print-inspect.dylan
  (classify-dylan-object, dylan-object-class, dylan-object-immediate-value):
   Handle the $dylan-tag-unichar case.
[rt] Call into the memory management APIs.

This updates the C runtime to call into the actual memory
management APIs rather than just have stubbed out entry
points.

Also, fix () parameter lists to be (void);
[rt] Remove primitive-gc-state and MMCollectCount.

These weren't used anywhere and the primitive had been disabled
long ago.
[rt] Fix warning in c-support.c.
[rt] Fix build error.
[rt] _GNU_SOURCE is defined by the build system.
[rt] Fix dependency info.
[rt] Fix warnings about int sizes.