[BuildTools] avoiding multiple generation of libtool scripts

[Andreas Waechter]

Hi

I have done a few changes in coin.m4 that (hopefully) will allow us to 
avoid the multiple generation of the libtool scripts (and the re-doing of 
all the tests) in the project subdirectories.

What happens now is that one can include the macro AC_COIN_CREATE_LIBTOOL 
in a packages base directories configure.ac file (instead of the 
AC_COIN_INIT_AUTOMAKE macro).  This will then run all compiler tests in 
the packages base directory and create the libtool script.

Now, if configure runs in a project subdirectory, it checks if it can find 
the libtool script in .., ../.., or ../../.. .  If it is found, all the 
libtool related checks are skipped, and the script is no longer created 
here.  If the libtool script is not detect in those directories, the tests 
are run and the script is created locally.

The nice thing is that we could add this into the stable/0.5 version 
without having everybody switching to the new version necessarily at the 
same time.  However, I would prefer some more testing on other platforms 
before putting it into stable.  One issue is that currently a Fortran 
compiler is required, but I will make that optional soon.

It would be great if you could try that at some point.  I have tested it 
with Bonmin on Linux and Cygwin.

Please let me know what you think.

Cheers

Andreas