Silent termination of openloops on ol_fatal hides possible errors

Hi,

I encountered the odd behaviour where our (GENEVA) tests pass when openloops does not find the proclib folder (admittedly a self inflicted setup problem). This possibly hides test failures since openloops exits in ol_fatal with an exit code of 0 instead of indicating the failure.

29:  #####################################################################
29:  #        ___                                          version 2.1.3 #
29:  #       /   \ ___  ____  _  _  |     __   __  ___   __    ___       #
29:  #       |   | |__| |__   |\ |  |    /  \ /  \ |__| /__    __/       #
29:  #       \___/ |    |___  | \|  |___ \__/ \__/ |    __/   /__        #
29:  #                                                                   #
29:  #####################################################################
29:  #       You are using OpenLoops 2 to evaluate loop amplitudes       #
29:  #                             Authors:                              #
29:  #       F. Buccioni, J.-N. Lang, J. Lindert, P. Maierhoefer,        #
29:  #                S. Pozzorini, M. Zoller, H. Zhang                  #
29:  #                                                                   #
29:  #         Please cite Eur.Phys.J. C79 (2019) no.10, 866             #
29:  #                     Phys. Rev. Lett. 108 (2012) 111601            #
29:  #                     Eur.Phys.J. C78 (2018) no.1, 70               #
29:  #                                                                   #
29:  #####################################################################
29: 
29:                                                             
29:          *******************************************        
29:          *              C O L L I E R              *        
29:          *                                         *        
29:          *        Complex One-Loop Library         *        
29:          *      In Extended Regularizations        *        
29:          *                                         *        
29:          *    by A.Denner, S.Dittmaier, L.Hofer    *        
29:          *                                         *        
29:          *              version 1.2.8              *        
29:          *                                         *        
29:          *******************************************        
29:                                                             
29: [OpenLoops] ERROR: register_process: proclib folder not found, check install_path or install libraries.
29/29 Test #29: CalcSCETppV012RegressionTest ..........   Passed    0.04 sec

Note also above that the STOP print was not shown due to running non-verbose, further obscuring the failure.

In the ol_fatal code https://gitlab.com/openloops/OpenLoops/-/blob/master/lib_src/olcommon/src/debug.F90#L111 I propose to change the single stop to call exit(1) such that it exits with a non-zero exit code (alternatively stop 1 or error stop 1, but see https://github.com/hoppet-code/hoppet/pull/2 for more details why call exit(1) is best, IMO).

Cheers, APN