Bug #3937  	fails to compile with both gcc 3.3.3/icc8
Bug #4728  	mysql couldn't be compiled using system readline (readline-4.3)


acinclude.m4:
  1. added defun MYSQL_CHECK_READLINE_DECLARES_HIST_ENTRY for last versions of readline and libedit
  2. added #undef __P in defuns MYSQL_CHECK_LIBEDIT_INTERFACE, MYSQL_CHECK_NEW_RL_INTERFACE
client/mysql.cc:
  1. added #undef __P before #include "readline/readline.h" because readline-4.2 declares own __P
  2. changed !defined(USE_LIBEDIT_INTERFACE) to !defined(HAVE_HIST_ENTRY) before declaring of own hist_entry
     because latest versions of libedit declare hist_entry too
cmd-line-utils/Makefile.am:
  added copyright header
configure.in:
  1. added comment for --with-readline/--with-libedit options
  2. added define for HAVE_HIST_ENTRY and macro to check it
  3. added AC_LANG_CPLUSPLUS before readline/libedit checks