package/openswan: not available on musl

After fixing the usual sys/cdefs.h and _P stuff the build still fails
because Openswan makes use of GLOB_ functions

/home/bernd/buildroot/br4/output/build/openswan-2.6.48/lib/libipsecconf/parser.l:200:29: error: ‘GLOB_BRACE’ undeclared (first use in this function)
      globresult = glob(try, GLOB_BRACE, NULL, &globbuf);
                             ^
/home/bernd/buildroot/br4/output/build/openswan-2.6.48/lib/libipsecconf/parser.l:200:29: note: each undeclared identifier is reported only once for each function it appears in
/home/bernd/buildroot/br4/output/build/openswan-2.6.48/lib/libipsecconf/parser.l:207:41: error: ‘GLOB_NOMAGIC’ undeclared (first use in this function)
       globresult = glob(try, GLOB_BRACE|GLOB_NOMAGIC, NULL, &globbuf);

https://github.com/xelerance/Openswan/blob/master/lib/libipsecconf/parser.l#L200
https://github.com/xelerance/Openswan/blob/master/lib/libipsecconf/parser.l#L207
[...]
                                         ^
which musl does not support:
http://www.openwall.com/lists/musl/2013/09/16/1

Fixes
http://autobuild.buildroot.net/results/70d/70da34c1528b51e92e9e60788f83733d70b33353/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>