Delete trailing whitespace in examples

Remove TABs from examples

added regexp for valid utf-8 strings to test files. Other changes are minor

Improve compilation to executables - use in mkmunge and regexp2dfa

There is a new --exe option to buildheap, and this allows me to get
rid of the --mktex option. To make the munge.exe default possible, I
do also have to add a --defaultout option.

Adjust build workflow for regexp2dfa in formal-languages/regular

The pattern of 'export object file then link' is sufficiently
stereotyped that we should provide it as a function in somewhere like
Systeml (or even in buildheap itself).

Remove trailing whitespace throughout examples/

Converted ML implementation of charsets to align with that used in HOL. Also replaced regexp2{c,java,sml} by a single regexp2dfa program.