Hotswapping the other direction: system goal removal
Improve on previous commit hotswapping, rm_sysgoal

rm_sysgoal() is non-operational when there are fewer than 3 system goals.
Notify user of limitations of current rm_sysgoal() implementation
Move autman.c to directory dedicated for such code
PKG: Script to build source distributions
Merge branch 'master' into hotswap
REL: version 0.8.0; first draft of hotswap routines
DOC TRIV
Init contrib/ directory
First introduction of a marker for initial nodes.  Default False.

Almost nothing uses it yet, except list dumping (automaton_io.c).
DOC TRIV
DOC TRIV
Mark initial states in synthesize(); extended DOT and JSON output
DOC TRIV
Implementation of verification model generation for Spin

The command-line flag for gr1c is -P.  It may eventually support
selection of the tool target, but will continue with present target
(Spin) as default.

Consult documentation for spin_aut_dump() (cf. src/automaton.h).
Note that the resulting Promela file is missing a never claim that
may be added using the formula near the top of the file (under "LTL
formula").  E.g., try

  $ ./gr1c -t txt -o foo.txt examples/trivial.spc -P > trivsoln.pml
  $ spin -f '!(...formula inside comments of trivsoln.pml...)' >> trivsoln.pml
  $ spin -a trivsoln.pml && gcc -DNOREDUCE -o pan pan.c && ./pan -a

Notice that the formula must be negated to create a never claim.
We then use Spin to try to find acceptance cycles, i.e., cycles in
which the negated formula is satisfied, i.e., cycles in which the
specification is violated.
DOC TRIV
Detect transition faults in Spin Promela models