Squashed 'sqscripter/' changes from f3f7645..00704c5

00704c5 Fix script file handle treated as if opened though if failed
6538456 Add interface to show compile error markers

git-subtree-dir: sqscripter
git-subtree-split: 00704c53bc43585e05ebaa7d4ab65c09a656f770
Merge commit '97f0c3f7afe0f0f46eea2a649123014486ef2cd4' into next2
Show Squirrel runtime errors in SqScripter window

Now it can show source file and position where an error has occurred,
which helps debugging greatly.