Feature/use umfpack dl func versions

Kilian Weishaupt authored 5 years ago and Christoph Grüninger committed 5 years ago

With the *_dl_* versions instead of the *_di_* versions UMFPACK will
not have a memory limit of just 2GB.

Timo Koch authored 5 years ago and Christoph Grüninger committed 5 years ago

The index type was previously hard-coded to int. However, we might
want to change the index type for compatibility with legacy interfaces
of other libraries such as UMFPack.
This patch makes the index type customizable and defaults to int
for full backward-compatibility