Removal of the 6.x kernel compat code from libc

[Slawa Olhovchenkov]

On Fri, Apr 17, 2015 at 10:59:42AM +0300, Konstantin Belousov wrote:

> Our libc changes in sync with the kernel, but switching of libc to use
> new interfaces means that upgrade of the userspace becomes the flag day.
> People usually add backward-compatible shims for libc to use older
> interfaces on old kernels.
> 
> There is no reason to keep the compat shims after many years of the
> transition.  Patch below purges the compat code for pre-r171219, which
> added pad-less versions of syscalls taking off_t, and for r177911, which
> handles the struct flock/oflock transition.  This is 6.x/7.x compat,
> we absolutely not support running HEAD libc on such old kernels.

In general, what purpose for leaving conditional compilation for
different versions in kernel/base sources?
subversion repo already store different version in correlation.