flex cleanup, silence errors

On the poudriere jail build, it was impossible to build world due to
flex errors.  I don't know what is different about the environments --
perhaps one has -Werror and the other doesn't.

In any case, the new flex makes a lot of complaints due to internally
generated functions, etc, and this cleans them all up at once.
Relocate Flexlexer.h to /usr/include

FlexLexer was placed in /usr/include/c++ but this is not the normal
location nor is it a search path for either base compiler.  I believe
this is a legacy that should have been changed when the c++ search
path changed.
Revert "gcc4x: Update README to remove format.c from patched list"

This reverts commit fc18d536e167227d9010b0ce3420f5d21aba5799.

%D was removed, true, but c-format.c is still patched.