syscalls.2: parisc Linux does not any longer emulate HP-UX

Initially it was planned that the parisc linux port would natively
support 32-bit HP-UX binaries, but this compatibility was never
reached and finally dropped with Linux kernel 3.14.

With that background, drop parisc from the list of of platforms
which supports it's proprietary operating-system.

Additional notes from mtk:

The most relevant commit from the Linux 3.14 change log was:

[[
commit f5a408d53edef3af07ac7697b8bc54a755628450
Author: Guy Martin <gmsoft@tuxicoman.be>
Date:   Thu Jan 16 17:17:53 2014 +0100

    parisc: Make EWOULDBLOCK be equal to EAGAIN on parisc

    On Linux, only parisc uses a different value for EWOULDBLOCK which
    causes a lot of troubles for applications not checking for both values.
    Since the hpux compat is long dead, make EWOULDBLOCK behave the same as
    all other architectures.
]]

Additional notes from Helge:

The patch above is the initial and most important one with which
we stopped the HP-UX compatibility.

Then, with this commit in kernel 3.18 there is no way back:
"parisc: Reduce SIGRTMIN from 37 to 32 to behave like
other Linux architectures"
commit 1f25df2eff5b25f52c139d3ff31bc883eee9a0ab

And in kernel 4.0 we finally dropped the HP-UX compat layer
from Linux kernel source code with the commit series
"parisc: hpux - Drop support for HP-UX binaries":
commit 04c1614977168fb8f002e2d81f704eeabe0c5ebd

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/syscalls.2

@@ -693,7 +693,7 @@ older system calls were superseded by newer ones,
 and this has been treated somewhat unsystematically.
 On platforms with
 proprietary operating-system emulation,
-such as parisc, sparc, sparc64, and alpha,
+such as sparc, sparc64, and alpha,
 there are many additional system calls; mips64 also contains a full
 set of 32-bit system calls.
 .PP