Update spec for 0.8: Malformed types cause runtime errors for as, is and catch clauses, as well as …

Update spec for 0.8: Malformed types cause runtime errors for as, is and catch clauses, as well as checked mode subtype tests. Scripts main must be in exported namespace of library (can be exported, but import alone is not enough). Document effect of @proxy on typechecking. Metadata cannot include types.

Committed: https://code.google.com/p/dart/source/detail?r=29775

[gbracha, 2013-11-01 22:18:36]

Committed patchset #1 manually as r29775 (presubmit successful).

[Johnni Winther, 2013-11-04 12:34:49]

https://codereview.chromium.org/54903010/diff/1/docs/language/dartLangSpec.tex
File docs/language/dartLangSpec.tex (right):

https://codereview.chromium.org/54903010/diff/1/docs/language/dartLangSpec.te...
docs/language/dartLangSpec.tex:5603: Since $i$ is not a type, a static warning
will be issue at the declaration of $j$. However, the program can be executed
without incident in production mode because he undeclared type $i$ is treated as
\DYNAMIC{}. However, in checked mode, the implicit subtype test at the
assignment will trigger an error at runtime.
'because he undeclared' -> 'because the undeclared'.