Add mingw32-libpcre as dependency

This enables us to compile git against libpcre.
And this makes thing like
```
git grep -P "\bpcre\b" HEAD
```
possible.
Which I already did in https://github.com/t-b/git/tree/use-libpcre. And all tests still pass with that too.
mingw32-libpcre-dev is needed to add pcre support into git, enabled with [this patch](https://github.com/t-b/git/tree/use-libpcre) this is required at compile time.
mingw32-libpcre-dll is needed at runtime.
I thought I use the main package name which pulls in dev and dll.

Or should I add the runtime dependency to the package xml file?