Log Message:
Changes 4.57:

A new, more efficient implementation of the dual simplex method
was included in the package. This new implementation replaces
the old one, which was removed.

Option sr_heur was added to struct glp_iocp to enable/disable
the simple rounding heuristic used by the MIP solver.

New API routine glp_at_error was added and documented.

Some minor typos were corrected in the GLPK documentation.

An example application program TSPSOL was added. It uses the
GLPK MIP optimizer to solve the Symmetric Traveling Salesman
Problem and illustrates "lazy" constraints generation. For more
details please see glpk/examples/tsp/README.