Merge commit 'origin/andrei/type_conversion'

Merge commit 'origin/andrei/type_conversion'

* commit 'origin/andrei/type_conversion':
  script parsing: fix bug in expression error checking
  core expr eval: various fixes
  news: update (new operators, expr. eval behaviour a.s.o.)
  core: new script operators: eq, ne, ieq, ine
  core expr eval: fix assoc., commut and 0 adding for +, ==
  core expr eval: minor ==/!= optimization
  core expr eval: internal == & != int and str only versions
  core expr eval: special handling for undef cmp expr
  core eval expr: cache undefined results too
  core expr eval:  str automatic conversion to int
  core expr eval: undef conversion to int and str
  core expr eval: defined @select