Changed the automake build process :
- ./configure.in
- ./sql/Makefile.am
to compile an instrumented parser for debug=yes or debug=full builds

Changed the (primary) runtime invocation of the parser :
- sql/sql_parse.cc
to generate bison traces in stderr when the DBUG "parser_debug" flag is set.


configure.in:
  WL#3432 (Compile the Parser with a --debug --verbose option)
  
  New Automake condition : MYSQL_CONF_DEBUG
sql/Makefile.am:
  WL#3432 (Compile the Parser with a --debug --verbose option)
  
  In Debug mode, compile sql_yacc.yy with --debug --verbose
sql/sql_parse.cc:
  WL#3432 (Compile the Parser with a --debug --verbose option)
  
  Conditionally turn the bison parser debug on at runtime.