linux(4): Move uselib() to i386

This obsolete system call is not supported by glibc. In ancient libc
versions (before glibc 2.0), uselib() was used to load the shared
libraries with names found in an array of names in the binary.
On Linux, since 3.15, this system call is available only when
the kernel is configured with the CONFIG_USELIB option.

It doesn't look like anyone needs this syscall for others Linuxulators,
so move it to the corresponding MD Linuxulator.

MFC after: 2 weeks

(cherry picked from commit 50c85a32d9c667779494850b6238b8d7ec13da75)