RFC: create defs from defs.in and adjust all test cases

[Alexandre Duret-Lutz]

I'd like to have tests/defs created from tests/defs.in by
configure.

This should simplify and fix many things.  

  - For instance we can use in the test suite the same perl as
    found by configure (this is not the case currently: the
    test suite will use PERL=perl even if the user ran
    `./configure PERL=python'...).

  - We can speed-up the test suite by factoring some tests out of
    defs.  Typically we would define EGREP and FGREP from
    ./configure instead of running the detection code in defs
    for each test case.

However having tests/defs in the build directory means *each*
test case should be changed.

   . $srcdir/defs

should become

   . ./defs

A nice side effect is that in an non-VPATH build, it will
allow test cases to be run individually like ordinary scripts
(well, for VPATH builds it's possible too but the test case must
be run from the directory where defs is).

While I'm patching each test case, it's probably the occasion to
add the missing copyright notice to each file.

So in summary I'm proposing to
  1. create tests/defs from tests/defs.in
  2. change each test case to include `./defs' instead of `$srcdir/defs'
  3. add the copyright notice to each test case

I'd like to do that this week.

Comments, objections?
-- 
Alexandre Duret-Lutz