#6 better after-command whitespace handling

[Oleg Paraschenko]

See also:

http://sourceforge.net/tracker/index.php?func=detail&aid=949178&group_id=102261&atid=631463

The current problem is:

<cmd name="a"/><cmd name="b"/>c

is converted to

\a{}\b{}c

but a better variant is

\a\b{}c

--

Introduce after-command state. Write "{}" only if next
symbol is not "{", "\", "/", "#" etc. Note that we ust
write "{}" in case of space, even if weak one.