Bison/flex version upgrade doesn't reconstruct oct-parse.cc

[Daniel J Sebald]

Because of an ancient version of a utility, I ran into an error with the 
lexical parsing:

parse-tree/oct-parse.cc: In function 'int yypull_parse(yypstate*, 
octave_base_parser&)':
parse-tree/oct-parse.cc:3977:14: error: 'yylex' was not declared in this 
scope

then updated Bison and flex to their most recent versions and eventually 
fixed the problem.

The one snag I ran into was the fact that the file oct-parse.cc is not 
updated or cleared by any of the common make processes going as far back 
as 'bootstrap'.

That is, I upgraded Bison, re-ran 'configure' and found that the 
generated file oct-parse.cc still indicated Bison version 2.4.3 in its 
header and--from the file date--was generated an hour prior to running 
'configure'.  Furthermore, 'make clean' doesn't remove the file. 
(Although, I should point out that my build directory is separate from 
the source tree.)  Therefore, updating Bison to 3.0.2 had no effect 
until I rebuilt from scratch with an empty configure tree.

Forcing that parser regeneration will probably cause recompilation of 
the file oct-parse.cc and some other files every time "make" is run. 
Would it be possible to have a little script that searches oct-parse.cc 
for the Bison version and if it doesn't produce the same result as the 
working version of Bison, then update the file?  Or is there a problem 
with that if someone builds from source files of the released version?

Should we at least remove the family of oct-parse.cc files with 'make 
clean'?

lex.cc       oct-parse.cc  oct-parse.output  pt-binop.df
lex.df       oct-parse.df  oct-parse.yy      pt-eval.df
oct-gperf.h  oct-parse.h   pt-arg-list.df    pt-mat.df

Dan