revert bison locations

Bison locations are not compatible with byacc and are not important
enough to break compatibility.
silence parser implicit function warnings

This is to silence warnings about yyset_in and yylex function declarations
missing.  I'd don't like to silence warnings, but if there's nothing I can
do about them then I don't want them showing up in the build output.
Merge branch 'byacc'
Update CHANGES and configure.ac for v2.1

This release includes fixes for make check, the needed files are
now included in the distribution, and the bison locations code was
removed to maintain compatibility with byacc.