While regtesting with [bitcoin-spock](https://github.com/msgilligan/bitcoin-spock) I noticed at some point the transaction creation via `sendtoaddress -> CreateTransaction()` fails, because the created transaction is larger than `MAX_STANDARD_TX_SIZE`.

During the process a lot of raw transactions are created, which have smallish outputs and when then using `sendtoaddress`, it appears to attempt to create a transaction that spends too many of those dust-ish outputs.

The transaction to create does not have many outputs, but it looks like it's caused by the coin selection, which selects too many inputs. Testing was done with a 0.9 branch, but on the first glimpse I believe this issue is as well be present in 0.10. If this is a known issue, and if there is already a guard against this behavior, I'd be happy about a hint.

Sorry in advance, I do not have a test script to reproduce this issue in an isolated manner. A potential fix would probably require to adjust the coin selection, so that it selects a combination of coins, which, in addition to the size of the rest of the transaction, is still smaller than the limit.

* param@[in]   nTargetValue    Subset sum target, not including change.
 * param@[out]  vfBest          Boolean vector representing the subset chosen that is closest to
 *                              nTargetValue, with indices corresponding to groups. If the ith
 *                              entry is true, that means the ith group in groups was selected.
 * param@[out]  nBest           Total amount of subset chosen that is closest to nTargetValue.
 * param@[in]   iterations      Maximum number of tries.
 */
static void ApproximateBestSubset(FastRandomContext& insecure_rand, const std::vector<OutputGroup>& groups,
                                  const CAmount& nTotalLower, const CAmount& nTargetValue,
                                  std::vector<char>& vfBest, CAmount& nBest, int iterations = 1000)
{
    std::vector<char> vfIncluded;
    /
    vfBest.assign(groups.size(), true);
    nBest = nTotalLower;
    for (int nRep = 0; nRep < iterations && nBest != nTargetValue; nRep++)
    {
        vfIncluded.assign(groups.size(), false);
        CAmount nTotal = 0;
        bool fReachedTarget = false;
        for (int nPass = 0; nPass < 2 && !fReachedTarget; nPass++)
        {
            for (unsigned int i = 0; i < groups.size(); i++)
            {
                /
                /
                /
                /
                /
                /