Provide killpg implementation.

Based on github PR#301 for Tandem NonStop.

configure.ac

@@ -1876,6 +1876,7 @@ AC_CHECK_FUNCS([ \
 	inet_ntoa \
 	inet_ntop \
 	innetgr \
+	killpg \
 	llabs \
 	localtime_r \
 	login_getcapbool \

openbsd-compat/bsd-misc.c

@@ -412,6 +412,14 @@ getsid(pid_t pid)
 }
 #endif
 
+#ifndef HAVE_KILLPG
+int
+killpg(pid_t pgrp, int sig)
+{
+	return kill(pgrp, sig);
+}
+#endif
+
 #ifdef FFLUSH_NULL_BUG
 #undef fflush
 int _ssh_compat_fflush(FILE *f)

openbsd-compat/openbsd-compat.h

@@ -82,6 +82,10 @@ int getpagesize(void);
 char *getcwd(char *pt, size_t size);
 #endif
 
+#ifndef HAVE_KILLPG
+int killpg(pid_t, int);
+#endif
+
 #if defined(HAVE_DECL_MEMMEM) && HAVE_DECL_MEMMEM == 0
 void *memmem(const void *, size_t, const void *, size_t);
 #endif