Revert changes relative to lib/*.[ch] recent renaming

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

  f871de0... build: make use of 76 lib/*.h renamed files
  ffd8e12... build: rename 76 lib/*.h files

This also reverts removal of redundant include guard (redundant thanks
to changes in above commits) done 2-12-2013, reverting 1 commit:

  c087374... curl_setup.h: remove redundant include guard

This also reverts renaming and usage of lib/*.c source files done
3-12-2013, reverting 3 commits:

  13606bb... build: make use of 93 lib/*.c renamed files
  5b6e792... build: rename 93 lib/*.c files
  7d83dff... build: commit 13606bbfde follow-up 1

Start of related discussion thread:

  http://curl.haxx.se/mail/lib-2013-01/0012.html

Asking for confirmation on pushing this revertion commit:

  http://curl.haxx.se/mail/lib-2013-01/0048.html

Confirmation summary:

  http://curl.haxx.se/mail/lib-2013-01/0079.html

NOTICE: The list of 2 files that have been modified by other
intermixed commits, while renamed, and also by at least one
of the 6 commits this one reverts follows below. These 2 files
will exhibit a hole in history unless git's '--follow' option
is used when viewing logs.

  lib/curl_imap.h
  lib/curl_smtp.h

1 files changed, 74 insertions, 0 deletions

diff --git a/lib/speedcheck.c b/lib/speedcheck.c
new file mode 100644
index 000000000..ca2323f57
--- /dev/null
+++ b/lib/speedcheck.c
@@ -0,0 +1,74 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "setup.h"
+
+#include <curl/curl.h>
+#include "urldata.h"
+#include "sendf.h"
+#include "multiif.h"
+#include "speedcheck.h"
+
+void Curl_speedinit(struct SessionHandle *data)
+{
+  memset(&data->state.keeps_speed, 0, sizeof(struct timeval));
+}
+
+CURLcode Curl_speedcheck(struct SessionHandle *data,
+                         struct timeval now)
+{
+  if((data->progress.current_speed >= 0) &&
+     data->set.low_speed_time &&
+     (Curl_tvlong(data->state.keeps_speed) != 0) &&
+     (data->progress.current_speed < data->set.low_speed_limit)) {
+    long howlong = Curl_tvdiff(now, data->state.keeps_speed);
+    long nextcheck = (data->set.low_speed_time * 1000) - howlong;
+
+    /* We are now below the "low speed limit". If we are below it
+       for "low speed time" seconds we consider that enough reason
+       to abort the download. */
+    if(nextcheck <= 0) {
+      /* we have been this slow for long enough, now die */
+      failf(data,
+            "Operation too slow. "
+            "Less than %ld bytes/sec transferred the last %ld seconds",
+            data->set.low_speed_limit,
+            data->set.low_speed_time);
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+    else {
+      /* wait complete low_speed_time */
+      Curl_expire(data, nextcheck);
+    }
+  }
+  else {
+    /* we keep up the required speed all right */
+    data->state.keeps_speed = now;
+
+    if(data->set.low_speed_limit)
+      /* if there is a low speed limit enabled, we set the expire timer to
+         make this connection's speed get checked again no later than when
+         this time is up */
+      Curl_expire(data, data->set.low_speed_time*1000);
+  }
+  return CURLE_OK;
+}