taking project name from directory name
now, with the exception of F_CPU and MCU and BAUD, one Makefile
can work for all projects
should be able to copy over, saving hassle.

to do this, every sub-project needed its own directory
so there's a few more created
also, care is taken to make sure all projects at 8MHz have
 corresponding 8MHz Makefiles:
   for f in `grep -s -l clock_div_1 Chapter*/*/*` ; do dirname $f ; done

Found a bunch of directories with multiple main files, split into
subdirs

Found multiple un-init-to-zero variables that were throwing compiler
warnings.  Cleaned these up.

all cleaned up and tested

But none of it substantive.  :)
Just moving global variable definitions / declarations around to make it
work with the new makefile structure.
(I was lax with where things were before b/c I was lumping all C files
together in compile phase.)

Catching lots of little bugs and complier warnings:
 mostly multiple main() functions in multiple files in same dir
 and uninitialized zero variables

Almost all solved by creating subdirectories and adding "=0" here and
there.

Exception is servo sundial code, which needed a deeper re-work because
of the (ab)use of global variables.

* post_makefile_review:
  Many changes in servo sundial code
  more zero-inits and multiple main directories
  Through chapter 06

Doesn't change functionality, but readability.

Thanks KaiserS0ze for pointing this out.

Thanks dComposer!