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[rt] Start splitting up the C run-time.
[rt] Allow building 32 bit on 64 bit host.
[io] Fix missing stream parameter.
[rt] Add back MMCollectCount for now.

This is here for the HARP builds to link correctly until we
re-generate the .o files for them.
[rt] Only do -fPIC on 64 bit.

This appears to break MPS on 32-bit platforms, but it isn't
strictly necessary there and we don't (yet) use MPS on
64-bit.
[jam] Set ARCH defs like we do for the runtime.
Adding a function stream-console?
Merge pull request #506 from iglennrogers/isatty

Adding a function stream-console?
[docs] Replace ``<foo>`` with :drm:`<foo>` for all DRM classes.
[io] Fix bug in accessor-console? on win32.
Merge pull request #507 from cgay/docs

[docs] Replace ``<foo>`` with :drm:`<foo>` for all DRM classes.
Use OPEN_DYLAN_PLATFORM_NAME to set LIB dirs.

OPEN_DYLAN_PLATFORM_NAME is available to JAM as TARGET_PLATFORM.

We were using OS and OSPLAT, but using OPEN_DYLAN_PLATFORM_NAME
will make things more consistent and work with things like
emscripten and the Java backend. It also makes cross-compilation
work again by just setting OPEN_DYLAN_PLATFORM_NAME and everything
else working from that.
Export target-platform-name, re-use it.
Rename OPEN_DYLAN_PLATFORM_NAME to OPEN_DYLAN_TARGET_PLATFORM.
Release notes for OPEN_DYLAN_TARGET_PLATFORM.
Merge pull request #505 from waywardmonkeys/cross-build-fixes

Use OPEN_DYLAN_PLATFORM_NAME to set LIB dirs.
find-registries() now takes platform-name.

It previously took architecture/operating system parameters which
we're working to get away from.
Merge pull request #508 from waywardmonkeys/find-registries

find-registries() now takes platform-name.
Remove extra default-build-script.

The generic in environment-protocols just existed to route to the
same thing in build-system, so get rid of the overhead / duplication.