configure: include all libraries in ssl-libs fetch

When compiling a collection of SSL libraries to link against (SSL_LIBS),
ensure all libraries are included. The call `--libs-only-l` can produce
only a subset of found in a `--libs` call (e.x. pthread may be excluded).
Adding `--libs-only-other` ensures other libraries are also included in
the list. This corrects select build environments compiling against a
static version of OpenSSL. Before the change, the following could be
observed:

    checking for openssl options with pkg-config... found
    configure: pkg-config: SSL_LIBS: "-lssl -lz -ldl -lcrypto -lz -ldl "
    configure: pkg-config: SSL_LDFLAGS: "-L/home/jdknight/<workdir>/staging/usr/lib -L/home/jdknight/<workdir>/staging/usr/lib "
    configure: pkg-config: SSL_CPPFLAGS: "-I/home/jdknight/<workdir>/staging/usr/include "
    checking for HMAC_Update in -lcrypto... no
    checking for HMAC_Init_ex in -lcrypto... no
    checking OpenSSL linking with -ldl... no
    checking OpenSSL linking with -ldl and -lpthread... no
    configure: WARNING: SSL disabled, you will not be able to use HTTPS, FTPS, NTLM and more.
    configure: WARNING: Use --with-ssl, --with-gnutls, --with-polarssl, --with-cyassl, --with-nss, --with-axtls, --with-winssl, or --with-darwinssl to address this.
    ...
    SSL support:      no      (--with-{ssl,gnutls,nss,polarssl,mbedtls,cyassl,axtls,winssl,darwinssl} )
    ...

And include the other libraries when compiling SSL_LIBS succeeds with:

    checking for openssl options with pkg-config... found
    configure: pkg-config: SSL_LIBS: "-lssl -lz -ldl -pthread -lcrypto -lz -ldl -pthread "
    configure: pkg-config: SSL_LDFLAGS: "-L/home/jdknight/<workdir>/staging/usr/lib -L/home/jdknight/<workdir>/staging/usr/lib "
    configure: pkg-config: SSL_CPPFLAGS: "-I/home/jdknight/<workdir>/staging/usr/include "
    checking for HMAC_Update in -lcrypto... yes
    checking for SSL_connect in -lssl... yes
    ...
    SSL support:      enabled (OpenSSL)
    ...

Signed-off-by: James Knight <james.d.knight@live.com>
Closes #3193
diff --git a/configure.ac b/configure.ac
index 80f8ae1..b0bd9a3 100755
--- a/configure.ac
+++ b/configure.ac
@@ -1623,7 +1623,7 @@
 
     if test "$PKGCONFIG" != "no" ; then
       SSL_LIBS=`CURL_EXPORT_PCDIR([$OPENSSL_PCDIR]) dnl
-        $PKGCONFIG --libs-only-l openssl 2>/dev/null`
+        $PKGCONFIG --libs-only-l --libs-only-other openssl 2>/dev/null`
 
       SSL_LDFLAGS=`CURL_EXPORT_PCDIR([$OPENSSL_PCDIR]) dnl
         $PKGCONFIG --libs-only-L openssl 2>/dev/null`