Allow one to change ANSI_QUOTES mode per thread and on the fly


sql/field.cc:
  Use new my_strntoxxx functions where function clears errno.
  Change variable names to 'not_used' for variables that is not used in function
sql/sql_base.cc:
  comment
sql/sql_lex.cc:
  Allow one to change ANSI_QUOTES mode per thread and on the fly
sql/sql_lex.h:
  Allow one to change ANSI_QUOTES mode per thread and on the fly
strings/ctype-simple.c:
  Changed my_strntoxxx functions to clear error number on start
  Changed my_strtod() to correctly set return error number
strings/ctype-utf8.c:
  Changed my_strntoxxx functions to clear error number on start
  Changed my_strtod() to correctly set return error number