configure: drop detection of stdint.h and inttypes.h

The current code uses macros from inttypes.h. There is no point in
detecting and selecting between stdint.h and inttypes.h as the latter is
always needed.

sysincl.h

@@ -36,6 +36,7 @@
 #include <float.h>
 #include <glob.h>
 #include <grp.h>
+#include <inttypes.h>
 #include <math.h>
 #include <netdb.h>
 #include <netinet/in.h>
@@ -63,14 +64,6 @@
 #include <sys/timex.h>
 #endif
 
-#ifdef HAVE_INTTYPES_H
-#include <inttypes.h>
-#elif HAVE_STDINT_H
-#include <stdint.h>
-#else
-/* Tough */
-#endif
-
 #ifdef FEAT_IPV6
 /* For inet_ntop() */
 #include <arpa/inet.h>