libre2c: found pathological case for constant-memory POSIX algorithms.

libre2c: found pathological case for constant-memory POSIX algorithms.

The regexp is ((a?){1,200})*, and the input string is just "a".

Takes quibic time in the size of counter. This is caused by quadratic-
time computation of precedence matrix on each step (the number of TNFA
states in the closure approaches TNFA size), multiplied by the length
of compared histores (which also approaches TNFA size). Trie-based
algorithms are not affected, but they consume memory proportional to
the length of the input string, and so are also not practical.