configure: re-order SSL libs when linking

When doing static builds, the ordering of libs is important, as the
linker does not back-pedal to previous libraries specified on the
command line to find missing symbols, and only searches for those
missing symbols in the following libs.

Thus, as -lssl needs symbols from -lcrypto, it needs to come before
-lcrypto.

And globally, we do *not* append new libraries, we prepend them.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

diff -durN a/configure.in b/configure.in
--- a/configure.in	2014-10-16 11:12:08.000000000 +0200
+++ b/configure.in	2015-05-30 15:44:25.540329788 +0200
@@ -133,12 +133,14 @@
     [AC_MSG_ERROR([header file <openssl/ssl.h> is required for OpenSSL, use --with-openssl-path=PATH])]
   )
   AC_CHECK_LIB([crypto],[CRYPTO_new_ex_data],
-    [SSL_LIBADD="$SSL_LIBADD -lcrypto"],
-    [AC_MSG_ERROR([library 'crypto' is required for OpenSSL])]
+    [SSL_LIBADD="-lcrypto $SSL_LIBADD"],
+    [AC_MSG_ERROR([library 'crypto' is required for OpenSSL])],
+    [$SSL_LIBADD]
   )
   AC_CHECK_LIB([ssl],[SSL_library_init],
-    [SSL_LIBADD="$SSL_LIBADD -lssl"],
-    [AC_MSG_ERROR([library 'ssl' is required for OpenSSL])]
+    [SSL_LIBADD="-lssl $SSL_LIBADD"],
+    [AC_MSG_ERROR([library 'ssl' is required for OpenSSL])],
+    [$SSL_LIBADD]
   )
   AC_SUBST(SSL_LIBADD)
 fi