Fix bugs in OpenSSL hook renaming.

libpq's exports.txt was overlooked in commit 36d108761, which the
buildfarm is quite unhappy about.

Also, I'd gathered that the plan included renaming PQgetSSLKeyPassHook
to PQgetSSLKeyPassHook_OpenSSL, but that didn't happen in the patch
as committed.  I'm taking it on my own authority to do so now, since
the window before beta1 is closing fast.

src/interfaces/libpq/fe-secure-openssl.c

@@ -1687,7 +1687,7 @@ PQdefaultSSLKeyPassHook_OpenSSL(char *buf, int size, PGconn *conn)
 }
 
 PQsslKeyPassHook_OpenSSL_type
-PQgetSSLKeyPassHook(void)
+PQgetSSLKeyPassHook_OpenSSL(void)
 {
 	return PQsslKeyPassHook;
 }