Add file download information window + SHA-256 + more checksums

I'm not the biggest fan of how the info window works, but it works
anyway, and it's easy to apply to *all* the download links.

Also decided to sign & checksum static binaries. Those are just as
important (if not more so) than the source tarballs.

Yes, I did verify that my copies of all the files were still in line
with the other checksums before creating the SHA256 checksums. :)

And I think I'm done fiddling with the site now; This is the last of my
planned changes. ...except that the site kinda sucks in text-mode
browsers now. Hmm. But how do I improve that?

dat/ncdc.md

@@ -6,7 +6,7 @@ interface.
 ## Get ncdc!
 
 Latest version
-:   1.21 ([dllink ncdc-1.21.tar.gz]
+:   1.21 ([ncdc-1.21.tar.gz](/download/ncdc-1.21.tar.gz)
     \- [changes](https://dev.yorhel.nl/ncdc/changes))
 
     Convenient static binaries for Linux:

dat/ncdu.md

@@ -9,7 +9,7 @@ POSIX-like environment with ncurses installed.
 ## Download
 
 Latest version
-:   1.14 ([dllink ncdu-1.14.tar.gz] - [changes](/ncdu/changes))
+:   1.14 ([ncdu-1.14.tar.gz](/download/ncdu-1.14.tar.gz) - [changes](/ncdu/changes))
 
     I also have convenient static binaries for Linux
     [i486](/download/ncdu-linux-i486-1.14.tar.gz) and

dat/tuwf.md

@@ -23,7 +23,7 @@ information and details.
 
 ## Download
 
-**Latest packaged version:** 1.2 ([dllink TUWF-1.2.tar.gz]
+**Latest packaged version:** 1.2 ([TUWF-1.2.tar.gz](/download/TUWF-1.2.tar.gz)
 \- [CPAN mirror](https://metacpan.org/release/TUWF))
 
 TUWF is also available on a git repository at