libc: fix MIPS N64 fork

fork() is broken for MIPS64 N64 ABI. You can check it with a simple
C program statically linked with qemu-mips64 user emulation.
Internally fork() is using the clone system call (at least with NPTL)
with 5 arguments. See ./libpthread/nptl/sysdeps/unix/sysv/linux/i386/fork.c.
The calling conventions for MIPS N32 and N64 allow to use up to 8 registers
for that. See http://en.wikipedia.org/wiki/Calling_convention#MIPS
This is correctly implemented in libc/sysdeps/linux/mips/bits/syscalls.h,
but not in libc/sysdeps/linux/mips/sysdep.h. fork.c uses the later one.
It seems that fork() works fine for MIPS64 N32 with just using the stack like
with the O32 case. There is a user of INLINE_SYSCALL with 7 arguments in
libc/sysdeps/linux/common/sync_file_range.c for MIPS64 N32, so I decided to
only use the macros for the MIPS64 N64 case. With this patch my uClibc based
Linux system boots up fine in qemu-system-mips64.

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
vfork: fix clone based version

The clone based version was introduced by commit

58570fc8e1fd601f15be5758ab95013d56771804
vfork: Use clone if arch does not have the vfork syscall

but the code was made unreachable by the previous commit

0a043c30ee71245dfe7c9d82d654312c5e1f6127
vfork: make all archs consistent

that adds a guard which require either __NR_vfork or __NR_fork
to be set.
Neither will be set on an arch that would need to use the
clone based version.

The double declaration of vfork was also introduced by
the merge of the two above mentioned patches.
The missing ; was present in the original patch.

CC: Markos Chandras <markos.chandras@imgtec.com>
CC: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
CC: Peter S. Mazinger <ps.m@gmx.net>
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
powerpc: syscall support up to 6 arguments

As reported by Kristof Provost.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>