core: Add thread-safe group info functions with dynamic buffers

Provides getgrgid, getgrnam, getpwuid & getpwnam replacements that are
thread safe (a la getgrgid_r() and friends) that internally
handle allocating big-enough buffers to avoid ERANGE errors
on large users or groups.

src/pulsecore/usergroup.h

@@ -0,0 +1,51 @@
+#ifndef foousergrouphfoo
+#define foousergrouphfoo
+
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2009 Ted Percival
+
+  PulseAudio is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as
+  published by the Free Software Foundation; either version 2.1 of the
+  License, or (at your option) any later version.
+
+  PulseAudio is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with PulseAudio; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#include <sys/types.h>
+
+#ifndef PACKAGE
+#error "Please include config.h before including this file!"
+#endif
+
+#ifdef HAVE_GRP_H
+
+struct group *pa_getgrgid_malloc(gid_t gid);
+void pa_getgrgid_free(struct group *grp);
+
+struct group *pa_getgrnam_malloc(const char *name);
+void pa_getgrnam_free(struct group *group);
+
+#endif /* HAVE_GRP_H */
+
+#ifdef HAVE_PWD_H
+
+struct passwd *pa_getpwuid_malloc(uid_t uid);
+void pa_getpwuid_free(struct passwd *passwd);
+
+struct passwd *pa_getpwnam_malloc(const char *name);
+void pa_getpwnam_free(struct passwd *passwd);
+
+#endif /* HAVE_PWD_H */
+
+#endif /* foousergrouphfoo */