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, 53 insertions, 0 deletions

diff --git a/src/shared/ratelimit.h b/src/shared/ratelimit.h
new file mode 100644
index 0000000000..a6443e7f87
--- /dev/null
+++ b/src/shared/ratelimit.h
@@ -0,0 +1,53 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#ifndef fooratelimithfoo
+#define fooratelimithfoo
+
+/***
+  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/>.
+***/
+
+#include "util.h"
+
+typedef struct RateLimit {
+        usec_t interval;
+        usec_t begin;
+        unsigned burst;
+        unsigned num;
+} RateLimit;
+
+#define RATELIMIT_DEFINE(_name, _interval, _burst)       \
+        RateLimit _name = {                              \
+                .interval = (_interval),                 \
+                .burst = (_burst),                       \
+                .num = 0,                                \
+                .begin = 0                               \
+        }
+
+#define RATELIMIT_INIT(v, _interval, _burst)             \
+        do {                                             \
+                RateLimit *_r = &(v);                    \
+                _r->interval = (_interval);              \
+                _r->burst = (_burst);                    \
+                _r->num = 0;                             \
+                _r->begin = 0;                           \
+        } while (false)
+
+bool ratelimit_test(RateLimit *r);
+
+#endif