... if insufficient space is available in the output buffer.

Also remove some superfluous code.

And improve an error message.

In anticipation of adding settings and stats.

configure checks if you have lcov & genhtml; these can be specified
with --with-lcov and/or --with-genhtml.

If they are available, the make target coverage can be executed:

- make clean, then make check with CC=gcc and CFLAGS set so that
  inputs for gcov/lcov are generated.

- lcov creates the src/coverage subdir and generates a targetfile
  there.

- genhtml generates HTML reports in src/coverage.

Also change the date outputs to include time zones.