Filled out the object file loader so it can load object files for several OSs and...

Filled out the object file loader so it can load object files for several OSs and architectures.

SConscript:
    Added ./libelf as an include search directory. There might be a better spot for this than where I put it.
arch/SConscript:
    Combined the linux_process.h and tru64_process.h into process.h. This allows each ISA to support processes from arbitrary OSs.
arch/alpha/SConscript:
    Added process.cc as a source file. It provides an implementation of createProcess, which takes an object_file object and creates the appropriate process object, or dies.
base/loader/elf_object.cc:
    Actually extract the OS and architecture from the elf file, rather than always guessing Alpha and Linux.
base/loader/object_file.hh:
    Added constants for SPARC, MIPS, and Solaris, and changed the include for the Addr type.
sim/process.cc:
    Pushed creation of specific process objects into the ISA specific code.

--HG--
extra : convert_revision : b4754e7ca8328672d07e1394c4d162e199606b53