sysdefs.h: Omit the conditionals around string.h and limits.h.

string.h is used unconditionally elsewhere in the project and
configure has always stopped if limits.h is missing, so these
headers must have been always available even on the weirdest
systems.

src/common/sysdefs.h

@@ -44,5 +44,4 @@
 
 // Some pre-C99 systems have SIZE_MAX in limits.h instead of stdint.h. The
 // limits are also used to figure out some macros missing from pre-C99 systems.
-#ifdef HAVE_LIMITS_H
 #include <limits.h>
@@ -48,5 +47,4 @@
 #include <limits.h>
-#endif
 
 // Be more compatible with systems that have non-conforming inttypes.h.
 // We assume that int is 32-bit and that long is either 32-bit or 64-bit.
@@ -153,5 +151,4 @@
 
 // string.h should be enough but let's include strings.h and memory.h too if
 // they exists, since that shouldn't do any harm, but may improve portability.
-#ifdef HAVE_STRING_H
 #include <string.h>
@@ -157,5 +154,4 @@
 #include <string.h>
-#endif
 
 #ifdef HAVE_STRINGS_H
 #	include <strings.h>