_PACKAGE sentinel: URL in DESCRIPTION that are separated by spaces are not parsed correctly

[daattali]

According to R-exts:

The ‘URL’ field may give a list of URLs separated by commas or whitespace

However, I noticed that if I use multiple URLs in DESCRIPTION with a space delimeter and then document using _PACKAGE, the resulting help file doesn't parse out the space and the resulting link is a (broken) concatenation of both URLs.

If I separate the URLs with a comma, then everything works as intended.

[hadley]

I think commas are so radically more common than whitespace, I'm happy to leave this as is minor infelicity of roxygen2.