Revert "linux: Move {f}xstat{at} to compat symbols"

This reverts commit 20b39d59 to move
{f}xstat{at} back to default symbols.  ABIs with default symbol version
of 2.33 or newer (such as riscv32) continue to just provide the stat
symbols.

The idea is to not force static libraries built against old glibc
to update against new glibcs (since they reference the old
{f}xstat{at} symbols).

Checked on x86_64-linux-gnu and i686-linux-gnu.