Add kore_pgsql_query_params().

This function uses PQsendQueryParams() instead of the normal PQsendQuery()
allowing you to pass binary data in a cleaner fashion.

A basic call would look something like:

char *mydata = "Hello";
size_t mydata_len = strlen(mydata);

kore_pgsql_query_params(&pgsql, req,
    "INSERT INTO foo VALUES($1::text)", KORE_PGSQL_FORMAT_TEXT, 1
    mydata, mydata_len, KORE_PGSQL_FORMAT_TEXT);

kore_pgsql_query_params() is variadic, allowing you to pass any
count of parameters where each parameter has the following:
	data pointer, data length, type of parameter.