The boot modules assembled by the generated boot_modules.s file is
accessed from core using struct Bm_header. Unfortunately the assembler
.long directive is synonym to .int [1] and thus has the same size as the
C++ int type and *not* long. Use the matching assembly type .quad in
boot_modules.s when generating the file for 64-bit platforms such as
x86_64.
[1] - https://sourceware.org/binutils/docs/as/Long.html
This patch contains the initial code needed to build and bootstrap the
base-hw kernel on x86 64-bit platforms. It gets stuck earlier
because the binary contains 64-bit instructions, but it is started in
32-bit mode. The initial setup of page tables and switch to long mode is
still missing from the crt0 code.
