uscan: version with dashes

[Nico Schlömer <nico.schloemer@gmail.com>]

Hello everyone,

a package now uses dashes instead of dots in upstream release tar
names. The watch file
```
version=4

opts=filenamemangle=s/.+\/trilinos-release-@ANY_VERSION@\.tar\.gz/trilinos-$1\.tar\.gz/
\
https://github.com/trilinos/Trilinos/tags
.*/trilinos-release-@ANY_VERSION@\.tar\.gz
```
continues to work, but reports
```
uscan info: Newest version of trilinos on remote site is 12-14-1,
local version is 12.12.1
uscan info:    => Only older package available from
      https://github.com/trilinos/Trilinos/archive/trilinos-release-12-14-1.tar.gz
```
How to replace the dashes with dots?

Cheers,
Nico