Update to 8.39. Introduce a "MAN3" option, to control installation of
~100 API manpages. Remove the bits about preventing coredumps on package
clusters during regression tests, because I'm not clear why the package
clusters would be running the regression tests. Rewrite the pkg-descr
using current text from pcre.org.
While here, clean up and reorganize the Makefile for simplicity and