psl.c: Include strings.h only if it is available

configure.ac

@@ -373,6 +373,9 @@ AC_CHECK_FUNCS([strndup clock_gettime fmemopen nl_langinfo])
 # check for dirent.h
 AC_HEADER_DIRENT
 
+# strings.h may not exist on WIN32
+AC_CHECK_HEADERS([strings.h])
+
 # Override the template file name of the generated .pc file, so that there
 # is no need to rename the template file when the API version changes.
 AC_CONFIG_FILES([Makefile

src/psl.c

@@ -64,7 +64,9 @@ typedef SSIZE_T ssize_t;
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <strings.h>
+#ifdef HAVE_STRINGS_H
+# include <strings.h>
+#endif
 #include <ctype.h>
 #include <time.h>
 #include <errno.h>