1.) Rename locore.s to locore.S (by repocopy), to be able to remove

1.) Rename locore.s to locore.S (by repocopy), to be able to remove
    special-case make rule
2.) Cleanups, remove superfluous expicit rules, add -nostdlib to LDFLAGS,
    remove -X and -g, remove -g from CFLAGS
3.) Add BINDIR
4.) Build install the loader help file, add an empty help.sparc64
5.) Change the default configuration to only support booting from disk
6.) Get libofw.a from a path relative ${.OBJDIR}, not ${.CURDIR}

Submitted by:	jake (1 - 5), obrien (6)