Updating to HEAD from 3.2 branch or pre-m4 import on 3.3 branch

[John Marino]

The update of M4, flex, and byacc together (all bootstrap tools) has 
made it challenging to build HEAD from previous release branches and 
those on the dev branch 3.3 that are set prior to the M4 import.

The following procedure *should* work for everyone that wishes to build 
the latest world:

Step 1:
Update /usr/src to HEAD (or at least to 
51dc126e91494039d4b328bfc3528ba18a49c317)

Step 2:
 > cd /usr/src/usr.bin/m4
 > make
 > make install
 > make clean cleandepend

Step 3:
Then do a full buildworld


Using gcc47 is more forgiving than gcc44 because the later sets -Werror. 
  If you do hit an "consider warnings as errors" type of break, you 
could always disable Werror by putting NO_WERROR=yes in the 
/etc/make.conf.  I do not believe it is necessary though.  With this 
technical I was able to upgrade from pre-m4 import as well as from the 
post-flex/pre-byacc imports.

I am sorry this is not as smooth as we'd hoped for, but flex and m4 are 
pretty well entwined in the source.

John