shared library calls exit()

[toeklk]

exit() is called in multiple parts of the library:

% grep -RiIw exit src
src/model/measurementmodel.cpp: exit(-BFL_ERRMISUSE);
src/model/measurementmodel.cpp: exit(-BFL_ERRMISUSE);
src/model/systemmodel.cpp: exit(-BFL_ERRMISUSE);
src/model/systemmodel.cpp: exit(-BFL_ERRMISUSE);
src/pdf/pdf.h: exit(-BFL_ERRMISUSE);
src/pdf/pdf.h: exit(-BFL_ERRMISUSE);
src/pdf/pdf.h: exit(-BFL_ERRMISUSE);
src/pdf/pdf.h: exit(-BFL_ERRMISUSE);
src/pdf/analyticconditionalgaussian.cpp: exit(-BFL_ERRMISUSE);
src/pdf/filterproposaldensity.cpp: exit(-BFL_ERRMISUSE);

Calling exit() is considered to be bad practice for shared libraries and
produces warnings by the packaging tools rpmlint [1] and lintian [2].

This bug report is part of an effort to package orocos-bfl for Fedora. Fedora's
packaging guidelines require to report such issues to upstream.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=469908
[2] https://lintian.debian.org/tags/shlib-calls-exit.html