Remove configure check for OpenSSL's SSL_get_current_compression()

This function has been added in OpenSSL 0.9.8, which is the oldest
version supported on HEAD, so checking for it at configure time is
useless.  Both the frontend and backend code did not even bother to use
it.

Reported-by: Daniel Gustafsson
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson, Tom Lane
Discussion: https://postgr.es/m/20191205083252.GE5064@paquier.xyz
Discussion: https://postgr.es/m/98F7F99E-1129-41D8-B86B-FE3B1E286881@yesql.se

configure

@@ -12094,7 +12094,7 @@ else
 fi
 
   fi
-  for ac_func in SSL_clear_options SSL_get_current_compression X509_get_signature_nid
+  for ac_func in SSL_clear_options X509_get_signature_nid
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"

configure.in

@@ -1186,7 +1186,7 @@ if test "$with_openssl" = yes ; then
      AC_SEARCH_LIBS(CRYPTO_new_ex_data, [eay32 crypto], [], [AC_MSG_ERROR([library 'eay32' or 'crypto' is required for OpenSSL])])
      AC_SEARCH_LIBS(SSL_new, [ssleay32 ssl], [], [AC_MSG_ERROR([library 'ssleay32' or 'ssl' is required for OpenSSL])])
   fi
-  AC_CHECK_FUNCS([SSL_clear_options SSL_get_current_compression X509_get_signature_nid])
+  AC_CHECK_FUNCS([SSL_clear_options X509_get_signature_nid])
   # Functions introduced in OpenSSL 1.1.0. We used to check for
   # OPENSSL_VERSION_NUMBER, but that didn't work with 1.1.0, because LibreSSL
   # defines OPENSSL_VERSION_NUMBER to claim version 2.0.0, even though it

src/include/pg_config.h.in

@@ -515,9 +515,6 @@
 /* Define to 1 if you have the `SSL_clear_options' function. */
 #undef HAVE_SSL_CLEAR_OPTIONS
 
-/* Define to 1 if you have the `SSL_get_current_compression' function. */
-#undef HAVE_SSL_GET_CURRENT_COMPRESSION
-
 /* Define to 1 if stdbool.h conforms to C99. */
 #undef HAVE_STDBOOL_H
 

src/include/pg_config.h.win32

@@ -373,9 +373,6 @@
 /* Define to 1 if you have the `SSL_clear_options' function. */
 #define HAVE_SSL_CLEAR_OPTIONS 1
 
-/* Define to 1 if you have the `SSL_get_current_compression' function. */
-#define HAVE_SSL_GET_CURRENT_COMPRESSION 1
-
 /* Define to 1 if stdbool.h conforms to C99. */
 #define HAVE_STDBOOL_H 1
 

src/include/port.h

@@ -446,10 +446,6 @@ extern void unsetenv(const char *name);
 extern void srandom(unsigned int seed);
 #endif
 
-#ifndef HAVE_SSL_GET_CURRENT_COMPRESSION
-#define SSL_get_current_compression(x) 0
-#endif
-
 #ifndef HAVE_DLOPEN
 extern void *dlopen(const char *file, int mode);
 extern void *dlsym(void *handle, const char *symbol);