grep RE repetition match curiosity

[Chris Beecroft]

The repetition match bug seems to provide strange results when zero is
used as the number of repetitions.

Given the file:
ab
azb
azzb

the regular expression pattern "az{0}b" acts as "az{0,1}b", i.e.,
returns the first two lines

likewise "az{0,0}b" acts like "az{0,1}b" and returns the first two lines
where only the first line should be expected.