Continuing the removal of compatibility code for old Linux kernel
versions, this patch increases the minimum kernel version from 2.4.1
to 2.4.21. This allows removal of all conditions on specific 2.4
kernel versions except for __ASSUME_TMPFS_NAME (where the comment says
2.4.20 but the code is actually testing against 2.4.26; I'll deal with
that when moving the required version to 2.6.0 rather than working out
whether actually 2.4.21 is enough there).
A fair amount of the patch deals with some macros defined and used
only for powerpc; could a powerpc maintainer review / test these
changes? (There are also ports changes to m68k/kernel-features.h, but
those are trivial.)
There was a single __ASSUME_NETLINK_SUPPORT test outside of
sysdeps/unix/sysv/linux, but it was only testing whether to define the
__no_netlink_support variable, previously used by some code that may
be built into nscd. Since the patch eliminates all uses of that
variable, the definition in nscd is no longer needed, so in fact all
__ASSUME_NETLINK_SUPPORT tests can go (there was no substantive use
relevant to non-Linux kernels) and so this patch removes them all and
the definition.
Tested x86 and x86_64.