src/lib/socket.c: fix build with libressl >= 3.5.0

Fix the following build failure with libressl >= 3.5.0:

/nvmedata/autobuild/instance-26/output-1/build/lua-cqueues-20200726/src/lib/socket.c: In function 'compat_SSL_is_server':
/nvmedata/autobuild/instance-26/output-1/build/lua-cqueues-20200726/src/lib/socket.c:188:12: error: invalid use of incomplete typedef 'SSL' {aka 'struct ssl_st'}
  188 |  return ssl->server != NULL;
      |            ^~
/nvmedata/autobuild/instance-26/output-1/build/lua-cqueues-20200726/src/lib/socket.c: At top level:
/nvmedata/autobuild/instance-26/output-1/build/lua-cqueues-20200726/src/lib/socket.c:2543:1: error: variable 'bio_methods' has initializer but incomplete type
 2543 | static BIO_METHOD bio_methods = {
      | ^~~~~~

Fixes:

http://autobuild.buildroot.org/results/823c9e27cdb8e01a048cb751287c01c5dc70f860

Signed-off-by: Fabrice Fontaine fontaine.fabrice@gmail.com

wahern / cqueues

src/lib/socket.c: fix build with libressl >= 3.5.0 #253