Fix Natvis not resolving for template args with negative constant

[iridinite]

Consider a template class with an integer type argument, that has a negative value as default:

template <int C = -1>
class Foo {};

The regex used to look for constants was missing support for the sign, and hence the above example would fail to parse Natvis properly.

[gregg-miskelly]

@iridinite did you sign the license agreement for this one? I think otherwise this one is ready to go. Could just be a problem with the bot.

[iridinite]

@gregg-miskelly Hm, that's odd; I didn't interact with the bot after #1396 since the result seems to be cached, not sure why it's hanging now. But yeah, I signed the CLA on behalf of Sony Interactive Entertainment. Let me know if I need to reset it somehow.

[gregg-miskelly]

@gregg-miskelly Hm, that's odd; I didn't interact with the bot after #1396 since the result seems to be cached, not sure why it's hanging now. But yeah, I signed the CLA on behalf of Sony Interactive Entertainment. Let me know if I need to reset it somehow.

Thanks for confirming! The check reran after I rebased, and it worked this time. So, odd, but at least it went away.