Bug 1734200

Description of problem:

The library version available in Fedora is old, and has problems compiling with projects that require C++17. There are new'er versions available released that solve many long-standing compilation issues on newer compilers and standards. 

Version-Release number of selected component (if applicable):
4.0.1.17.fc30

How reproducible:

Always.

Steps to Reproduce:
1. Try to compile a uWebsockets program that requires -std=c++17 with libpqxx

cc -DLIBUS_NO_SSL -flto -O3 -c -IuSockets/src uSockets/src/*.c uSockets/src/eventing/*.c
g++ -DLIBUS_NO_SSL -DUWS_NO_ZLIB -flto -O3 -c -std=c++17 -L/usr/lib64 -lpqxx -Isrc -IuSockets/src examples/HelloWorld.cpp

#include "App.h"

#include <pqxx/pqxx>


int main() {

      pqxx::connection c("postgresql://localhost");

        /* Overly simple hello world app */
        uWS::App().get("/*", [](auto *res, auto *req) {
            res->end("Hello world!");
        }).listen(3000, [](auto *token) {
            if (token) {
                std::cout << "Listening on port " << 3000 << std::endl;
            }
        }).run();

        std::cout << "Failed to listen on port 3000" << std::endl;
}


Actual results:
/usr/include/pqxx/result.hxx:135:35: error: ISO C++17 does not allow dynamic exception specifications


Expected results:

clean compilation

Additional info:

https://github.com/jtv/libpqxx/issues/103