Remove tinytest casts that were suppressing them.

Fix for #11825.

These are actually tests for #311.  It appears to me that we didn't
fix #311 properly when we thought we did in 475eb5d6; instead, the
real fix was 05eff35a, a few minutes earlier.

Fixes bug 11805; bugfix on 0.2.5.4-alpha.

Possible fix for bug 11648.

Should help speed up mingw builds by a percent or two.

Now that we have a scripts/* directory, let's put the scripts we use
for generating C there.

This may let us know if we're hitting 7164 because of an
hte_hash-corruption situation proposed by "cypherpunks" in bug
11737.

Since this is critical-path, let's tune the value we pass to
csiphash a little so it fits into one whole round.

Reported by cypherpunks.

Fix for #11761; bugfix on 0.2.3.13-alpha where we made ht.h stop using
_identifiers.

Fixes ticket 11750.