Mark function md5() as deprecated and compile md5.c again

Quote from issue #15:

> libcgi contains an implementation of the md5 hash function, however
> its not used inside the library itself and the status regarding
> license or potential security issues (despite the weekness of md5
> itself) is not clear. If a user needs md5 he or she could get it from
> a specialized library.

Although md5 is deprecated (#15) we can not simply remove the code from
the API. Do that later.

The HAVE_MD5 macro is useless, that was a relict from the old autotools
build and actually meant »build with md5«, so we can simply drop the
build time generated file and that macro.

Fixes: 0643151
Signed-off-by: Alexander Dahl <post@lespocky.de>

src/CMakeLists.txt

@@ -2,19 +2,14 @@
 # Copyright 2013,2016,2018 Alexander Dahl <post@lespocky.de>
 #
 
-configure_file(
-	"${CMAKE_CURRENT_SOURCE_DIR}/config.h.cmake.in"
-	"${CMAKE_CURRENT_BINARY_DIR}/config.h"
-)
-
 set(CGI_SRC
 	base64.c
 	cgi.c
 	cookie.c
 	error.c
 	general.c
 	list.c
-	#	md5.c
+	md5.c
 	session.c
 	string.c
 )

src/cgi.h

@@ -23,11 +23,21 @@
 
 #include <stdio.h>
 
+#if defined(__GNUC__)
+#define CGI_DEPRECATED __attribute__ ((deprecated))
+#elif defined(_MSC_VER)
+#define CGI_DEPRECATED __declspec(deprecated)
+#elif defined(__clang__)
+#define CGI_DEPRECATED __deprecated
+#else
+#pragma message("WARNING: You need to implement CGI_DEPRECATED for this compiler")
+#define CGI_DEPRECATED
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-
 // general purpose linked list. Actually isn't very portable
 // because uses only 'name' and 'value' variables to store data.
 // Problably, in a future release, this will be replaced by
@@ -81,7 +91,7 @@ extern char *stripslashes(char *str);
 extern char *str_base64_encode(char *str);
 extern char *str_base64_decode(char *str);
 extern char *recvline(FILE *fp);
-extern char *md5(const char *str);
+CGI_DEPRECATED char *md5(const char *str);
 extern char *cgi_ltrim(char *str);
 extern char *cgi_rtrim(char *str);
 extern char *cgi_trim(char *str);

src/md5.c

@@ -23,16 +23,13 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "error.h"
 #include "cgi.h"
 
 /** @ingroup libcgi_general
 * @{
 */
 
-#if HAVE_MD5
-
 #ifndef MD5_H
 #define MD5_H
 
@@ -95,7 +92,6 @@ char *md5(const char *str)
 	// returning a encrypted string
 	return tmp;
 }
-#endif
 
 /*=======================================================================*/