Write dumb math.c; various corrections

I heaved in an algorithm for popcnt() by Henry Warren. It ought to be more
efficient than my improvised loop.

Make the top-level asm target first.

Refactor naive.h and naive_read.h so that we can add some namespace to them
in order to include naive.h and math.h simultaneously without redefinitions.
It's rather ugly to use in this case but fully compatible to the old files.

Some doulbe-underscore functions in naive.h and naive_read.h got new
semantics - better ones. Namely __{prev,next}_number(), __is_composite() and
__next_prime() (which was created for this purpose): they can have distinct
struct numbers passed in now so that we don't have to use pt->pt_cur for
everything. These files are again a hellish mess now but there's not enough
time left to do things tidily. I need to come to an end with the paper until
Jan 23. Maybe I'll clean them up when I'm too tired to do new things...

BTW, I believe get_nth_prime() was buggy. It didn't clear pt->pt_cur before
it moved relative to it. I only glanced at the git diff but it should have
yielded wrong numbers where pt->pt_cur was already poluted with a value > 2.

Fix simple/rpt.c. It used bytes instead of words to count so it reported
wrong values at the end of each list. I wonder why it didn't crash once and
why it uses home-brew bit fiddling instead of the neat interface... I'll
have to correct that somewhen.

Write dumb math.c under new simple/math_dumb/ directory. This is for the
paper because the real fully-dynamic math.c is too complex to be treated in
the paper and time's too short for both _now_.

After all, I got the idea behind user/compress.c back to my mind - thank
heavens. I documented it quickly and renamed the file to pc.c (for prime
compressed).

Rename m2npt to ptconv. It is supposed to convert in either direction.

Add dist.awk which takes the output of rpt and computes the distance of
successive primes. Did you know that there are 34 numbers between p_21{8,7}?

Update Copyright information.

Write a lambda-prime-fast.c based on the expansion of the partial sum of
Lambda'. The name is currently misleading. It is not faster at all; just
iterative instead of recursive - but comparatively slow. This must be an
issue with the power set computation... It is be nevertheless possible that
for large T, it gets superior... I tested for 1000000 with both and didn't
get satisfying results (not even close to actually results) with either one.

I think I can refactor the power set algorithm to take advantage of
previously computed subsets of the power set but this takes some time. I see
no way I could calculate pi(10e24) until Jan 23.
Finish dumb math

Reduce stack usage of dumb math.c by going backwards through the sand
instead of buffering composites.

Make it not get SIGBUS anymore. The old size was used in math.c to
initialise the sand after the actual prime table was truncated by __polish()
so as the table crosses page boundaries and was then shrinked to below one
or more such pages, SIGBUS was delivered on access of those.

Optimise the thing a bit and add benchmarks for the paper. I'm finally done
with it.

.gitignore some more files.