Ok, when checking for old-style SSLeay headers we cannot just use

AC_CHECK_HEADERS() and the action-if-found since that action is run even if
just one of the six headers is found and I just now fell over a case with
a duplicate file name (a krb4 implementation with an err.h file).

I converted the check to manually make sure three of the headers are present
before considering them fine.

configure.ac

@@ -947,9 +947,18 @@ if test X"$OPT_SSL" != Xno; then
         AC_DEFINE(USE_OPENSSL, 1, [if OpenSSL is in use]))
 
       if test $ac_cv_header_openssl_x509_h = no; then
-        AC_CHECK_HEADERS(x509.h rsa.h crypto.h pem.h ssl.h err.h,
+        dnl we don't use the "action" part of the AC_CHECK_HEADERS macro
+        dnl since 'err.h' might in fact find a krb4 header with the same
+        dnl name
+        AC_CHECK_HEADERS(x509.h rsa.h crypto.h pem.h ssl.h err.h)
+
+        if test $ac_cv_header_x509_h = yes && 
+           test $ac_cv_header_crypto_h = yes &&
+           test $ac_cv_header_ssl_h = yes; then
+          dnl three matches
           curl_ssl_msg="enabled (OpenSSL)"
-          OPENSSL_ENABLED=1)
+          OPENSSL_ENABLED=1
+        fi
       fi
     fi