Implement bgStartsWith()
Implement bgstrStartsWith()
Fix more wrong argument order errors
Minor changes
Merge remote-tracking branch 'hainp/master'
Rename strIndexOf() to bgstrIndexOf()
Yet another wrong argument order ==
Introduce bgstrheap type
Refactor flatten()

Use a list of bgstrheap to store intermediary output instead of
overwritting the bgstr output itself.
Another test in main()