Created Pgsql::Transaction class for handling of transactions. It auto rollsback if no commit has been done.

Also moved some code out of the connection files to their own files.

pgsql/Pgsql_Canceller.cpp

@@ -0,0 +1,43 @@
+#include "Pgsql_Canceller.h"
+
+namespace Pgsql {
+
+	Canceller::Canceller(PGcancel *c)
+		: m_cancel(c)
+	{}
+
+	Canceller::Canceller(Canceller&& rhs)
+		: m_cancel(rhs.m_cancel)
+	{
+		rhs.m_cancel = nullptr;
+	}
+
+	Canceller& Canceller::operator=(Canceller&& rhs)
+	{
+		if (m_cancel) {
+			PQfreeCancel(m_cancel);
+		}
+		m_cancel = rhs.m_cancel;
+		rhs.m_cancel = nullptr;
+		return *this;
+	}
+
+	Canceller::~Canceller()
+	{
+		if (m_cancel) {
+			PQfreeCancel(m_cancel);
+		}
+	}
+
+	bool Canceller::cancel(std::string *error)
+	{
+		const int errbuf_size = 256;
+		char errbuf[errbuf_size];
+		bool res = PQcancel(m_cancel, errbuf, errbuf_size);
+		if (!res && error) {
+			*error = errbuf;
+		}
+		return res;
+	}
+
+}