Log Message:
tex-cweb{,-doc}: update to 4.2

In the course of the "2021 TeX tuneup", Don Knuth kindly transferred the
responsibility for CWEB to me; see the original CWEB home page
(https://www-cs-faculty.stanford.edu/~knuth/cweb.html), section "CWEB
4.0".

This first new release draws heavily on the multi-decade work collected in
my "CWEBbin" project (https://github.com/ascherer/cwebbin).  I moved
(almost) all stuff from the "*-patch.*" changefiles into the new CWEB
sources and applied all of the "*-ansi.*" changes as well.

Moreover, I made "common.h" the full interface of "common.w" \ 
in order to
avoid code redundancy.  And I tried to fix as many of the bugs reported by
email to DEK and/or tex-k at tug.org.

In total, "make; make cautiously; make fullmanual" runs flawlessly with
GCC on Linux and with CLang on MacOS.  And with the help of the remaining
stuff in the "CWEBbin" project, "CWEB" is smoothly \ 
integrated in "TeX
Live".