added generated symbols (symbols-*.cpp) to CLEANFILES

this was broken in #de616e362ccd56aae8b26a08d9520ab9132a060f
avoid narrowing-conversion warning in C++11

 * as of gcc 4.7.2, -Wnarrowing is in -Wall
ensure that expressions.eval(true) pops the brace "operator"

test case: 1<()>
 * an empty brace (or content that does not leave anything on the stack)
   resulted in the brace op to be left on the stack which makes the op stack
   inconsistent
don't abort on unexpected semicolon (break from loop)

the question remains what to do then.
FIXME: consult TECO standard
Merge branch 'master' of https://github.com/rhaberkorn/sciteco
fixed URL in .gitmodules