Use soci in some places:

* Brings the soci subtree into rippled.
* Validator, peerfinder, and SHAMapStore use new soci backend.
* Optional postgresql backend for soci (if POSTGRESQL_ROOT env var is set).

src/ripple/app/data/DummySociDynamicBackend.cpp

@@ -0,0 +1,59 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012-2015 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+/** Stub functions for soci dynamic backends.
+
+    Ripple does not use dynamic backends, and inclduing soci's
+    dynamic backends compilcates the build (it requires a generated
+    header file and some macros to be defines.)
+*/
+
+#include <BeastConfig.h>
+
+#include <ripple/app/data/SociDB.h>
+
+// dummy soci-backend
+namespace soci {
+namespace dynamic_backends {
+// used internally by session
+backend_factory const& get (std::string const& name)
+{
+    throw std::runtime_error ("Not Supported");
+    backend_factory* nullBF{nullptr};
+    return *nullBF;  // deref nullptr - but we already threw
+};
+
+// provided for advanced user-level management
+std::vector<std::string>& search_paths ()
+{
+    static std::vector<std::string> empty;
+    return empty;
+};
+void register_backend (std::string const&, std::string const&){};
+void register_backend (std::string const&, backend_factory const&){};
+std::vector<std::string> list_all ()
+{
+    return {};
+};
+void unload (std::string const&){};
+void unload_all (){};
+
+}  // namespace dynamic_backends
+}  // namespace soci
+