FEAT: initialized FreeBSD support branch.
Set the ident-osabi field properly for FreeBSD and Linux.
Export symbols for executables as well.
Add FreeBSD support.
Merge pull request #728 from rmn64k/freebsd

FreeBSD support for Red
FEAT: support for read/write access on CPU's general-purpose registers added to Red/System.

Usage:
    system/cpu/<reg>
    system/cpu/<reg>: <value>

<reg>:
    - IA-32: eax, ebx, ecx, edx, esp, ebp, esi, edi
    - ARM: r0 - r15
Merge branch 'freebsd' of github.com:red/red into freebsd
Add Red runtime FreeBSD API.
Add #case Red/System compiler directive.
Restructure simple-io.
Add FreeBSD stat struct to simple-io.
Merge remote-tracking branch 'upstream/freebsd' into freebsd

Get access to cpu registers.
Add access to the edx cpu register in start.reds.
Register the rtld cleanup routine on FreeBSD.
Merge pull request #729 from rmn64k/freebsd

Freebsd
Remove %BSD.reds and put the MacOSX definition in %darwin.reds.

We could probably have a common %BSD.reds for the other *BSDs even
if some of their structures and siginfo codes differ. MacOSX is
different enough that it makes sense to split it out.

The non MacOSX signal handling code didn't work so I removed it.
Add FreeBSD signal handling and initialization to %freebsd.reds.
Merge pull request #732 from rmn64k/freebsd

Freebsd
Add definitions for POSIX signal numbers.
Use the signal definitions in the POSIX runtime.