core:  move private prototypes in .c files

Link: https://github.com/GeneAssembly/biosal/issues/731
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
engine:  move private prototypes in .c files

Link: https://github.com/GeneAssembly/biosal/issues/731
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
examples:  move private prototypes in .c files

Link: https://github.com/GeneAssembly/biosal/issues/731
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
performance:  move private prototypes in .c files

Link: https://github.com/GeneAssembly/biosal/issues/731
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
genomics: move private prototypes in .c files

Link: https://github.com/GeneAssembly/biosal/issues/731
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
gc: put private functions in .c file

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>