so that the user can see whether it's going to be reasonably
accurate or not. There are two parts to this:
1) Use of #error and #warning in optiboot.c, for when the error is large.
2) Since you can't get the compiler to spit out actual numbers, create a
new target "baudcheck" that does. This is somewhat complicated by the
possibile non-availability of the usual development tools in the user
environment, so baudcheck.c is run through the avr-gcc preprocessor, and
produces a shell script.
http://code.google.com/p/optiboot/issues/detail?id=79