PSL before and abort operators

[Blebowski]

Currently NVC fails on code that contains PSL before operator:

WITHOUT_ABORT_a : assert (always a -> next (b before a));

with

** Error: unexpected identifier while parsing FL property, expecting one of **, union or )
    > ../src/psl_abort.vhd:33
    |
 33 |   WITHOUT_ABORT_a : assert (always a -> next (b before a));
    |                                                 ^^^^^^ this token was unexpected

and the abort operator:

WITH_ABORT_0_a : assert (always a -> next (b)) abort c;

with

** Error: unexpected identifier while parsing PSL or concurrent assertion statement, expecting ;
    > ../src/psl_abort.vhd:36
    |
 36 |   WITH_ABORT_0_a : assert (always a -> next (b)) abort c;
    |                                                  ^^^^^ this token was unexpected

Steps to reproduce are the same repo as other recently opened issues, with following differences:

1. Git hash: 3b6aad6e85ee69a13a0f5663aab2bdb0b4f052f4
2. make psl_abort or make psl_before