[Help-glpk] Add a hook for xassert

[Collette Yann]

Hello,

I'm currently writing an interface between glpk and scilab (see 
http://www.scilab.org).
My interface is working fine, but for some problems, glpk emits an 
assert which made scilab to hangs.

I have seen a preceding post where somebody adviced to catch the ABORT 
signal to avoid the hang.

I think a better solution should be to add 2 hooks:
- one to catch the assert message and allow to display this message in 
scilab (like the glp_term_hook)
- one to customize the way we exit from glpk (like replacing the abort 
call by a Scierror(999,"Assertion triggered\n") in scilab).

I think this should be useful because glpk still hangs on some problems 
(see the benchmark for LP at http://plato.asu.edu/ftp/lpfree.html and 
for MIP at http://plato.asu.edu/ftp/milpf.html).

YC