A major overhaul to adopt to recent changes. It now passes all tests.

Note:
- All test results haven't been inspected in detail to see if they are correct.
- Some result set printing seems to have the wrong field width; most notably
  date/time fields and type fields (e.g. "int(4)").
- There are still some valgrind complaints, but they seem to be in assert() or
  in libmysql.


tests/client_test.c:
  A major overhaul to adopt to recent changes:
  
  - SHOW TABLE result has changed (more columns)
  - EXPLAIN result has VAR_STRING types now
  - Added missing mysql_bind_result() calls
  - Adopted to mysql_fetch_column() semantics: Don't use same pointers in MYSQL_BIND
    structs for fetch_column as for binding.
  - Removed a number of duplicated calls to tests
  - Added missing initialization of MYSQL_BIND structs fields (lenght fields),
    to shutup valgrind.