Stop calling _init/_fini methods from crt1 for dynamic binaries. Do
call preinit, init and fini arrays methods from crt1 for static binaries.

Mark new crt1 with FreeBSD-specific ELF note.

Move some common crt1 code into new MI file ignore_init.c, to reduce
duplication. Also, conservatively adjust nearby sources for style.

Reviewed by: kan
Tested by: andrew (arm), flo (sparc64)
MFC after: 3 weeks