Part of this went upstream as https://github.com/uim/uim/commit/99fd890fa601b81ff99e5e0f1977fe309f56b90e.

The rest was done in https://github.com/uim/uim/pull/198.
--- a/configure.ac
+++ b/configure.ac
@@ -601,6 +601,7 @@ if test "x$ac_cv_func_snprintf" = xyes; then
 	AC_RUN_IFELSE(
 		[AC_LANG_SOURCE([[
 #include <stdio.h>
+#include <stdlib.h>
 int main(void){char b[5];snprintf(b,5,"123456789");exit(b[4]!='\0');}
 		]])],
 		[AC_MSG_RESULT(yes)],
--- a/m4/openssl.m4
+++ b/m4/openssl.m4
@@ -76,6 +76,7 @@ AC_MSG_CHECKING([OpenSSL header version])
 AC_RUN_IFELSE(
 	[AC_LANG_SOURCE([[
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <openssl/opensslv.h>
 #define DATA "conftest.sslincver"
@@ -156,7 +157,9 @@ AC_ARG_WITH(openssl-header-check,
 AC_MSG_CHECKING([whether OpenSSL's headers match the library])
 AC_RUN_IFELSE(
 	[AC_LANG_SOURCE([[
+#include <stdlib.h>
 #include <string.h>
+#include <openssl/crypto.h>
 #include <openssl/opensslv.h>
 int main(void) { exit(SSLeay() == OPENSSL_VERSION_NUMBER ? 0 : 1); }
 	]])],
@@ -220,8 +223,8 @@ int main(void) { DTLSv1_method(); }
 AC_MSG_CHECKING([if programs using OpenSSL functions will link])
 AC_LINK_IFELSE(
 	[AC_LANG_SOURCE([[
-#include <openssl/evp.h>
-int main(void) { SSLeay_add_all_algorithms(); }
+#include <openssl/crypto.h>
+int main(void) { OpenSSL_version_num(); }
 	]])],
 	[
 		AC_MSG_RESULT(yes)