[ruby/openssl] ssl: remove OpenSSL::ExtConfig

This module was introduced in 2015 for internal use within this library.
Neither of the two constants in it is used anymore. I don't think we
will be adding a new constant in the foreseeable future, either.

OPENSSL_NO_SOCK is unused since commit ruby/openssl@998d66712a78 (r55191).
HAVE_TLSEXT_HOST_NAME is unused since commit ruby/openssl@4eb4b3297a92.

ruby/openssl@eed3894bda

ext/openssl/ossl_ssl.c

@@ -33,7 +33,6 @@
 } while (0)
 
 VALUE mSSL;
-static VALUE mSSLExtConfig;
 static VALUE eSSLError;
 VALUE cSSLContext;
 VALUE cSSLSocket;
@@ -2591,16 +2590,6 @@ Init_ossl_ssl(void)
      */
     mSSL = rb_define_module_under(mOSSL, "SSL");
 
-    /* Document-module: OpenSSL::ExtConfig
-     *
-     * This module contains configuration information about the SSL extension,
-     * for example if socket support is enabled, or the host name TLS extension
-     * is enabled.  Constants in this module will always be defined, but contain
-     * +true+ or +false+ values depending on the configuration of your OpenSSL
-     * installation.
-     */
-    mSSLExtConfig = rb_define_module_under(mOSSL, "ExtConfig");
-
     /* Document-class: OpenSSL::SSL::SSLError
      *
      * Generic error class raised by SSLSocket and SSLContext.
@@ -2763,8 +2752,6 @@ Init_ossl_ssl(void)
      */
     rb_attr(cSSLContext, rb_intern_const("session_remove_cb"), 1, 1, Qfalse);
 
-    rb_define_const(mSSLExtConfig, "HAVE_TLSEXT_HOST_NAME", Qtrue);
-
     /*
      * A callback invoked whenever a new handshake is initiated on an
      * established connection. May be used to disable renegotiation entirely.
@@ -2956,10 +2943,8 @@ Init_ossl_ssl(void)
      */
     cSSLSocket = rb_define_class_under(mSSL, "SSLSocket", rb_cObject);
 #ifdef OPENSSL_NO_SOCK
-    rb_define_const(mSSLExtConfig, "OPENSSL_NO_SOCK", Qtrue);
     rb_define_method(cSSLSocket, "initialize", rb_f_notimplement, -1);
 #else
-    rb_define_const(mSSLExtConfig, "OPENSSL_NO_SOCK", Qfalse);
     rb_define_alloc_func(cSSLSocket, ossl_ssl_s_alloc);
     rb_define_method(cSSLSocket, "initialize", ossl_ssl_initialize, -1);
     rb_undef_method(cSSLSocket, "initialize_copy");