use copied strerror() messages and autoconfigured sys_nerr value

auto/unix

@@ -109,37 +109,13 @@ ngx_feature_test="char buf[1]; ssize_t n; n = pwrite(1, buf, 1, 0)"
 . auto/feature
 
 
-ngx_feature="strerror_r()"
-ngx_feature_name="NGX_HAVE_STRERROR_R"
-ngx_feature_run=yes
-ngx_feature_incs="#include <string.h>"
+ngx_feature="sys_nerr"
+ngx_feature_name="NGX_SYS_NERR"
+ngx_feature_run=value
+ngx_feature_incs='#include <stdio.h>'
 ngx_feature_path=
 ngx_feature_libs=
-ngx_feature_test="char buf[1024]; long n; n = strerror_r(1, buf, 1024);
-                  if (n < 0 || n > 1024) return 1;"
-. auto/feature
-
-
-# GNU style strerror_r() returns not length, but pointer
-
-ngx_feature="gnu style strerror_r()"
-ngx_feature_name="NGX_HAVE_GNU_STRERROR_R"
-ngx_feature_run=yes
-ngx_feature_incs="#include <string.h>"
-ngx_feature_path=
-ngx_feature_libs=
-ngx_feature_test="char buf[1024]; long n; n = strerror_r(1, buf, 1024);
-                  if (n >= 0 && n < 1024) return 1;"
-. auto/feature
-
-
-ngx_feature="sys_errlist[]"
-ngx_feature_name="NGX_HAVE_SYS_ERRLIST"
-ngx_feature_run=yes
-ngx_feature_incs="#include <stdio.h>"
-ngx_feature_path=
-ngx_feature_libs=
-ngx_feature_test="int n = sys_nerr; const char *p = sys_errlist[1];"
+ngx_feature_test='printf("%d", sys_nerr);'
 . auto/feature