do/while loops are double-counted in Generic.Metrics.CyclomaticComplexity

[MarkBaker]

Both while loops and do/while loops should increment the Cyclomatic Complexity score by one, because there are two paths through the code in both cases.

In the case of a while loop, the while code block will only be executed if the while condition is met, otherwise code execution will branch over the while code block. This gives just two branches in the code.

while ($condition) {            |\
    ...                         | \
    ...                         | /
}                               |<
                                v

When calculating the score, the T_WHILE token is recognised, and increases the CYC value correctly by one.

For a do/while loop, the do code block will always be executed at least once, and code execution may then branch back to repeat execution of that block, or may continue on through the code based on the while condition. This also has only two branches in the code.

do {                            |<
    ...                         | \
    ...                         | /
} while ($condition);           |/
                                |
                                v

However, when calculating the score, the sniff checks for both the T_DO and the terminating T_WHILE tokens, incrementing CYC by two (once for each token) in the do/while loop, rather than just by one (as it should).

This double-count error can easily be eliminated by removing the increment for the T_DO token.

Note that some the existing tests also erroneously assume that do/while should increment the CYC count by two, so they also require modification.