disable concat in hsql and enable it in FunctionForVoltDB, and test case...

...s
I am concerned about efficiency -- the need to make multiple copies of the left hand string.
I would prefer an implementation that 
1) loops once to calculates the total size, 
2) allocates a char vector of the total size,
3) loops a second time to set the bytes in the char vector
4) constructs a temp string value from the char vector and length