feature request: excluding lines with a regex, e.g. to exclude closing braces

[kforner]

cf #488

For some reasons independent from kcov, some false negatives are output by kcov, for example the closing brace of functions. Currently the --exclude-line only searches for exact sub-strings (cf https://github.com/SimonKagstrom/kcov/blob/master/src/filter.cc#L107), so it is difficult to only ignore closing braces.

A nice enhancement would be to support matching with a regex. Maybe a new option --exclude-line-pattern, or a syntactic way to signal that the --exclude-line value is a regex.