Make psignal prototype in libiberty match that in glibc.

Fixes:

gcc-2.95.3-glibc-2.1.3/binutils-2.15/libiberty/strsignal.c: In function `psignal':
gcc-2.95.3-glibc-2.1.3/binutils-2.15/libiberty/strsignal.c:563: argument `signo' doesn't match prototype
/usr/include/signal.h:131: prototype declaration
gcc-2.95.3-glibc-2.1.3/binutils-2.15/libiberty/strsignal.c:563: argument `message' doesn't match prototype
/usr/include/signal.h:131: prototype declaration
gcc-2.95.3-glibc-2.1.3/binutils-2.15/libiberty/strsignal.c:568: warning: comparison between signed and unsigned
mprotect... make[1]: *** [strsignal.o] Error 1
make[1]: Leaving directory `/export/hda3/dkegel/queue/jobdir.produser_cpsm17/crosstool-0.32/build/i686-unknown-linux-gnu/gcc-2.95.3-glibc-2.1.3/build-binutils/libiberty'
make: *** [all-libiberty] Error 2

when building on red hat 7.1
though it's a bit of a mystery why libiberty's psignal is being compiled at
all, since red hat 7.1's glibc supports psignal (hence the error message)

--- binutils-2.17/libiberty/strsignal.c.old	2005-04-18 13:57:40.000000000 -0700
+++ binutils-2.17/libiberty/strsignal.c	2005-04-18 13:59:09.000000000 -0700
@@ -536,7 +536,7 @@
 
 /*
 
-@deftypefn Supplemental void psignal (unsigned @var{signo}, char *@var{message})
+@deftypefn Supplemental void psignal (int @var{signo}, const char *@var{message})
 
 Print @var{message} to the standard error, followed by a colon,
 followed by the description of the signal specified by @var{signo},