util: move all to shared/ and split external dependencies in separate internal libraries

Before:
  $ ldd /lib/systemd/systemd-timestamp
  linux-vdso.so.1 =>  (0x00007fffb05ff000)
  libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f90aac57000)
  libcap.so.2 => /lib64/libcap.so.2 (0x00007f90aaa53000)
  librt.so.1 => /lib64/librt.so.1 (0x00007f90aa84a000)
  libc.so.6 => /lib64/libc.so.6 (0x00007f90aa494000)
  /lib64/ld-linux-x86-64.so.2 (0x00007f90aae90000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007f90aa290000)
  libattr.so.1 => /lib64/libattr.so.1 (0x00007f90aa08a000)
  libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f90a9e6e000)

After:
  $ ldd systemd-timestamp
  linux-vdso.so.1 =>  (0x00007fff3cbff000)
  libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f5eaa1c3000)
  librt.so.1 => /lib64/librt.so.1 (0x00007f5ea9fbb000)
  libc.so.6 => /lib64/libc.so.6 (0x00007f5ea9c04000)
  /lib64/ld-linux-x86-64.so.2 (0x00007f5eaa3fc000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007f5ea9a00000)
  libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f5ea97e4000)

1 files changed, 69 insertions, 0 deletions

diff --git a/src/shared/set.h b/src/shared/set.h
new file mode 100644
index 0000000000..885780c4c0
--- /dev/null
+++ b/src/shared/set.h
@@ -0,0 +1,69 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#ifndef foosethfoo
+#define foosethfoo
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+/* Pretty straightforward set implementation. Internally based on the
+ * hashmap. That means that as a minor optimization a NULL set
+ * object will be treated as empty set for all read
+ * operations. That way it is not necessary to instantiate an object
+ * for each set use. */
+
+#include "hashmap.h"
+
+typedef struct Set Set;
+
+Set *set_new(hash_func_t hash_func, compare_func_t compare_func);
+void set_free(Set* s);
+void set_free_free(Set *s);
+Set* set_copy(Set *s);
+int set_ensure_allocated(Set **s, hash_func_t hash_func, compare_func_t compare_func);
+
+int set_put(Set *s, void *value);
+int set_replace(Set *s, void *value);
+void *set_get(Set *s, void *value);
+void *set_remove(Set *s, void *value);
+int set_remove_and_put(Set *s, void *old_value, void *new_value);
+
+int set_merge(Set *s, Set *other);
+void set_move(Set *s, Set *other);
+int set_move_one(Set *s, Set *other, void *value);
+
+unsigned set_size(Set *s);
+bool set_isempty(Set *s);
+
+void *set_iterate(Set *s, Iterator *i);
+void *set_iterate_backwards(Set *s, Iterator *i);
+void *set_iterate_skip(Set *s, void *value, Iterator *i);
+
+void set_clear(Set *s);
+void *set_steal_first(Set *s);
+void* set_first(Set *s);
+void* set_last(Set *s);
+
+#define SET_FOREACH(e, s, i) \
+        for ((i) = ITERATOR_FIRST, (e) = set_iterate((s), &(i)); (e); (e) = set_iterate((s), &(i)))
+
+#define SET_FOREACH_BACKWARDS(e, s, i) \
+        for ((i) = ITERATOR_LAST, (e) = set_iterate_backwards((s), &(i)); (e); (e) = set_iterate_backwards((s), &(i)))
+
+#endif