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

tests/server/resolve.c

@@ -51,8 +51,8 @@
 #include "curlx.h" /* from the private lib dir */
 #include "util.h"
 
-/* include curl_memdebug.h last */
-#include "curl_memdebug.h"
+/* include memdebug.h last */
+#include "memdebug.h"
 
 static bool use_ipv6 = FALSE;
 static const char *ipv_inuse = "IPv4";
@@ -136,7 +136,7 @@ int main(int argc, char *argv[])
       hints.ai_socktype = SOCK_STREAM;
       hints.ai_flags = AI_CANONNAME;
       /* Use parenthesis around function to stop it from being replaced by
-      the macro in curl_memdebug.h */
+      the macro in memdebug.h */
       rc = (getaddrinfo)(host, "80", &hints, &ai);
     }