Move sourced/shared scripts to boot-*-common
Rearrange common definitions in each boot script to make them more
similar
Add common support for %ARCH% substitutions in DI_WWW_HOME
Fix boot-alpha to use which_deb when looking for aboot
Merge mips* together, using boot-mips-common
Currently the ins loader (mostly HMC loading into an LPAR) only
supports kernels up to 8 MiB. The jessie kernel has 11 MiB, which
does not fit and hence gets its tail overwritten by the initrd
(root.bin) loaded at this address. This change bumps the load
address to 16 MiB, which should allow for some more growth of
the kernel.
Signed-off-by: Philipp Kern <pkern@debian.org>