Make common usecase for negative path matches more discoverable: add "-exclude" option (ccfind)

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ccfind supports excluding certain sub-directories, .e.g.:

$ ccfind -path='(^>*/tests/)' -text=1.2.3

excludes all "tests" directories from searching for text "1.2.3".

To make this feature more discoverable a "-exclude" option should be provides,
as for instance "rsync" has, which would simplify above cryptic command to:

$ ccfind -exclude='tests/' -text=1.2.3

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Feature added in v2.3.0