3.1 branch libstdc++ problem with ctime on hpux

[law@redhat.com]

libstdc++-v3 currently fails to build on the GCC 3.1 branch with this
failure:



In file included from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/c
wchar:51,
                 from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/b
its/fpos.h:45,
                 from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/i
osfwd:46,
                 from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/i
os:44,
                 from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/i
stream:44,
                 from /scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/f
stream:45,
                 from /portal/fall/gcc-3.1/libstdc++-v3/src/globals.cc:30:
/scr/gcc-3.1/hppa2.0w-hp-hpux11.00/libstdc++-v3/include/ctime:75: `ctime' not 
   declared


The underlying problem is "ctime" provided by libstdc++-v3 defines "_CTIME",
which is a special symbol for HPUX -- if _CTIME is defined, then HPUX will
not provide a prototype for the "ctime" function.

The only reason _CTIME is defined apparently is to deal with including
"ctime" multiple times. 

I'm not sure how you want to fix this, but it is critical for GCC 3.1.

FWIW, there's a lot of other special symbols like that in HPUX.  So it's
entirely possible we'll run into other similar problems.

jeff