bpo-32598: Use autoconf to detect usable OpenSSL (#5242)

Add https://www.gnu.org/software/autoconf-archive/ax_check_openssl.html
to auto-detect compiler flags, linker flags and libraries to compile
OpenSSL extensions. The M4 macro uses pkg-config and falls back to
manual detection.

Add autoconf magic to detect usable X509_VERIFY_PARAM_set1_host()
and related functions.

Refactor setup.py to use new config vars to compile _ssl and _hashlib
modules.

Signed-off-by: Christian Heimes <christian@python.org>
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 380dd1b..c5eec7e 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -64,6 +64,13 @@
 #include "openssl/rand.h"
 #include "openssl/bio.h"
 
+/* Set HAVE_X509_VERIFY_PARAM_SET1_HOST for non-autoconf builds */
+#ifndef HAVE_X509_VERIFY_PARAM_SET1_HOST
+#  if !defined(LIBRESSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER > 0x1000200fL
+#    define HAVE_X509_VERIFY_PARAM_SET1_HOST
+#  endif
+#endif
+
 /* SSL error object */
 static PyObject *PySSLErrorObject;
 static PyObject *PySSLCertVerificationErrorObject;