Backend makefile cleanup. make maintainer-clean is now completely

functional.

Handle include file installation in src/include/Makefile

genbki.sh improvements: Don't substitute anything by config.status,
instead pass in AWK and CPP through environment. Change calling
convention to support named output files, so we get to see error
messages on stderr.

Rename bootstrap template files and install them into PREFIX/share.
Update initdb to that effect and other readability improvements
in initdb.