[Tachyon-list] x86 64 bits support

All the tests are now executing correctly in 32 and 64 bits. The makefile target assumes the 64 bit version of d8 is named d8_64.

I also tested only the parser, bootstrapped in 32 and 64 bits, respectively with 'make bt-parser' and 'make bt-parser64'. There is a multiplication overflow when executing the 32 bit version but the 64 bit version parses and pretty print fibonacci correctly.

Tomorrow I'll look at the full boostrap.

Erick