Static PIE support for alpha.

Static PIE support for alpha.

This adds alpha-specific first-pass GOT relocation code to boot.h.
The assembly code is pure magic.  The numeric register
names don't make it easier to understand (or compare with the
equivalent ld.so code).  Unfortunately the assembler only understands
a few symbolic register names.

Renames the crt0.o entry point to __start.  Our compiler was already using
__start and the linker will soon follow.

ok kurt@