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

lib/formdata.h

@@ -0,0 +1,98 @@
+#ifndef HEADER_CURL_FORMDATA_H
+#define HEADER_CURL_FORMDATA_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2010, 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.
+ *
+ ***************************************************************************/
+
+enum formtype {
+  FORM_DATA,    /* form metadata (convert to network encoding if necessary) */
+  FORM_CONTENT, /* form content  (never convert) */
+  FORM_CALLBACK, /* 'line' points to the custom pointer we pass to the callback
+                  */
+  FORM_FILE     /* 'line' points to a file name we should read from
+                   to create the form data (never convert) */
+};
+
+/* plain and simple linked list with lines to send */
+struct FormData {
+  struct FormData *next;
+  enum formtype type;
+  char *line;
+  size_t length;
+};
+
+struct Form {
+  struct FormData *data; /* current form line to send */
+  size_t sent;           /* number of bytes of the current line that has
+                            already been sent in a previous invoke */
+  FILE *fp;              /* file to read from */
+  curl_read_callback fread_func; /* fread callback pointer */
+};
+
+/* used by FormAdd for temporary storage */
+typedef struct FormInfo {
+  char *name;
+  bool name_alloc;
+  size_t namelength;
+  char *value;
+  bool value_alloc;
+  size_t contentslength;
+  char *contenttype;
+  bool contenttype_alloc;
+  long flags;
+  char *buffer;      /* pointer to existing buffer used for file upload */
+  size_t bufferlength;
+  char *showfilename; /* The file name to show. If not set, the actual
+                         file name will be used */
+  bool showfilename_alloc;
+  char *userp;        /* pointer for the read callback */
+  struct curl_slist* contentheader;
+  struct FormInfo *more;
+} FormInfo;
+
+int Curl_FormInit(struct Form *form, struct FormData *formdata );
+
+CURLcode Curl_getformdata(struct SessionHandle *data,
+                          struct FormData **,
+                          struct curl_httppost *post,
+                          const char *custom_contenttype,
+                          curl_off_t *size);
+
+/* fread() emulation */
+size_t Curl_FormReader(char *buffer,
+                       size_t size,
+                       size_t nitems,
+                       FILE *mydata);
+
+/*
+ * Curl_formpostheader() returns the first line of the formpost, the
+ * request-header part (which is not part of the request-body like the rest of
+ * the post).
+ */
+char *Curl_formpostheader(void *formp, size_t *len);
+
+char *Curl_FormBoundary(void);
+
+void Curl_formclean(struct FormData **);
+
+CURLcode Curl_formconvert(struct SessionHandle *, struct FormData *);
+
+#endif /* HEADER_CURL_FORMDATA_H */