slightly clean up some of the changes made when ELF64 support went in

adapt ELF-using compat code to use new ELF definitions/code. At this point,
these are restricted to 32-bit ELF, and should be severely cleaned.

Define execv() and execve() consistently across emulations.
Do path name translation.

Simplify and add comments.

- Pass the Elf32_Ehdr in the linux probe function, and use it!

Since linux binaries are (mostly) always compiled with gcc, look for
the gcc signature in the .comment section header: "\0 GCC: (GNU) "

- Pass the Elf32_Ehdr in the linux probe function, and use it!

Since linux binaries are (mostly) always compiled with gcc, look for
the gcc signature in the .comment section header: "\0 GCC: (GNU) ".
I've changed the probe order in kern/exec_elf.c to probe for linux ELF
binaries first and fall back to SVR4 binaries. This makes statically
linked binaries work for both linux and svr4. Note that gcc-compiled
svr4 binaries, still contain the operating system signature first and
then the GCC signature, so there is no conflict. Yes this is a hack.

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Prototyping changes.

Prefix names of system call implementation functions with `sys_'.

Make system calls conform to a standard prototype and bring those
prototypes into scope.

Rearrange #includes.

Use compat_util.[ch].

* Changed to use generic ELF code from kern/exec_elf.c (which was taken
from the svr4 exec code plus the linux compat mods)
* Include file change
* Add multicast sockopts (from John Brezak)

Don't forget to acknowledge that all the ELF stuff was taken from
Christos' svr4 code.

* Make Linux ELF binaries work. Lots of code duplication, but it will have to do
for now.
* Add a sanity check in linux_uselib

Generate the new ps_strings format.

- added struct emul to all emulations.
- removed all setup functions.
- added copyargs() functions where needed.

Handle Linux signal tramp code differently. Some changes because of the
now seperate Linux signal trampoline code. Add linux_sigreturn to
syscalls.master.

Added a few more system calls.
More consistent alternate root file semantics throughout.

Added Linux compat code.