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