Simplify build process by getting rid of bison/flex dependencies.

Fixes both MSVC and autotools (automake 1.12+).

Revert "Abort autogen.sh when automake 1.12+ is found."

This reverts commit 978ed8f1f90544162c327f334bd590cd7b944ce1.
Should now work with automake 1.11+

fixes ticket:3887
fixes ticket:3538
closes ticket:3950