configurable support for ELF core dumps

   text    data     bss     dec     hex filename
3330172  529036  190556 4049764  3dcb64 vmlinux-baseline
3325552  528912  190556 4045020  3db8dc vmlinux-no-elf

add/remove: 0/8 grow/shrink: 0/0 up/down: 0/-4424 (-4424)
function                                     old     new   delta
fill_note                                     32       -     -32
maydump                                       58       -     -58
dump_seek                                     67       -     -67
writenote                                    180       -    -180
elf_dump_thread_status                       274       -    -274
fill_psinfo                                  308       -    -308
fill_prstatus                                466       -    -466
elf_core_dump                               3039       -   -3039

Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>