This satisfies a symbol reference created with:
.symver __libc_vfork, vfork@GLIBC_2.0
where `__libc_vfork' has not been defined or referenced. In this case
the `vfork@GLIBC_2.0' reference is supposed to be discarded, however a
bug present in GAS since forever causes an undefined symbol table entry
to be created. This in turn triggers a problem in the linker that can
manifest itself by link errors such as:
ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'
The GAS and linker bugs need to be resolved, but we can avoid them too
by providing a `__libc_vfork' definition just like our other platforms.
[BZ #17485]
* sysdeps/unix/sysv/linux/mips/vfork.S (__libc_vfork): Define.