Merge x86 boot options in x86/boot(8) and add undocumented UEFI options
We were supposed to keep the option list in x86/boot(8), x86/dosoot(8)
and x86/pxeboot(8) in sync, but it did not happen, hence it may work
better with all the options in x86/boot(8). Also add the undocumented
UEFI boot options.
sync with head.
for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.
this commit was splitted into small chunks to avoid
a limitation of cvs. ("Protocol error: too many arguments")