stm32f429i-disco, stm3240g-eval, stm3220g-eval, stm3210e-eval:  Eliminate duplicate Make.defs files.

Build System:  It is no longer necessary to have a unique Make.defs file for each configuration.  A board may share a common Make.defs file in the scripts directory.

ipforward.h:  Add some forward references that are needed when CONFIG_NETDEV_MULTINIC is not enabled.

Fix some errors in ipforward.h when CONFIG_NET_STATISTICS is enabled, but CONFIG_NETDEV_MULTINIC is not

tools/refresh.sh: Now runs make savedefconfig before copying the new defconfig file in place;  Also, added a new option --defaults.  Since the number of defaults that you now have to answer is so large, the option lets you just accept the default values.  So it works just like --slilent but still prompts you for the decision to save or discard the new defconfig file.

Update configure.sh, configure.bat, configure.c:  With compressed format, part of the installation requires that we run 'make olddefconfig' to restore the uncompressed defconfig format.  Also, while I was at it, I also added options to select host platform on configure command line.