Fix compiler errors with strict C23 standards

Fix missing/misplaced '#include "config.h"' statements. Fixes missing
  function prototypes, unknown type definitions, etc. Allows configuration
  of GCC with CFLAGS="-std=c23" instead of using default -std=gnu23.

Don't know about CLANG, MSVC, MinGW, etc, but using
gwb@stitch:~> gcc --version
gcc (SUSE Linux) 15.1.1 20250714
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Hamlib can compile in strict C23 mode, or previous standard levels.

lib/precise_time.c

@@ -20,6 +20,7 @@
 // along with fldigi.  If not, see <http://www.gnu.org/licenses/>.
 // ---------------------------------------------------------------------
 
+#include "config.h"
 #include <errno.h>
 #include <time.h>
 #include <sys/time.h>

rigs/barrett/barrett.c

@@ -19,6 +19,7 @@
  *
  */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

rigs/dummy/dummy.c

@@ -20,6 +20,7 @@
  *
  */
 
+#include "config.h"
 // cppcheck-suppress *
 #include <stdint.h>
 // cppcheck-suppress *

rigs/dummy/flrig.c

@@ -20,6 +20,7 @@
 *
 */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>             /* String function definitions */

rigs/dummy/netrigctl.c

@@ -19,6 +19,7 @@
  *
  */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>  /* String function definitions */

rigs/dummy/quisk.c

@@ -19,6 +19,7 @@
  *
  */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>  /* String function definitions */

rigs/dummy/tci1x.c

@@ -19,6 +19,7 @@
 *
 */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>             /* String function definitions */

rigs/dummy/trxmanager.c

@@ -20,6 +20,7 @@
  *
  */
 
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>             /* String function definitions */

security/AESStringCrypt.c

@@ -28,6 +28,7 @@
  * BUT NOT LIMITED TO, LOSS OF DATA OR DATA BEING RENDERED INACCURATE.
  */
 
+#include "config.h"
 #include <stdio.h>
 #include <string.h>
 

src/sleep.c

@@ -35,10 +35,10 @@
  * \note parameters are same as man page for each
  *
  */
+#include "hamlib/config.h"
 #include <unistd.h>
 #include <errno.h>
 #include <pthread.h>
-#include "hamlib/config.h"
 #include "sleep.h"
 
 #ifdef  __cplusplus

tests/rigtestmcastrx.c

@@ -1,3 +1,4 @@
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>