dropt 2.0.1

• Fixed contact information and other minor comment and documentation tweaks.
• Minor code refactoring.

dropt 2.0.0

• Modified the signature for option handlers to accept a pointer to the
  matched dropt_option entry. Custom option handlers will need to be
  adjusted.
• Added a new field to dropt_option to store additional callback data.
  This warranted renaming the existing handler_data member. Code that
  initialized dropt_option members by name will need to be adjusted.
• Added a new dropt_handle_const handler that uses the new callback data
  to store predefined values.
• Reformatted code and comments.

dropt 1.1.1

• Fixed a build issue with gcc with optimizations enabled.
• Changed dropt_error to be an unsigned int type instead of an enum
  type to avoid potential comparison warnings with custom error values.
• Fixed dropt_misuse to terminate in debug builds. (I accidentally
  disabled termination in dropt 1.1.0.)
• Added a Makefile for clang.
• Added an INSTALL file with build instructions.
• Added a droptxx_example.cpp file as a C++ sample program.
• Changed the directory layout a bit.