Add update-sources.sh script for PlayScript.Dynamic
Improve handling of arithmetic in the dynamic runtime

This addresses edge case issues like handling of strings, null, and
undefined.

Also moves the logic to a T4 template to reduce duplicate code.
Fix ToString for null and undefined
Return NaN instead of 0 for addition with undefined

The other arithmetic operators were doing the right thing, but addition
was missed
Make sure appending null to a string appends "null"

In C# casting null to a string results in an empty string, but in
ActionScript it gets the string value of "null"
Fix arithmetic operations involving null/undefined
Add support for unit tests in .cs files

Useful for debugging failures in the mcs test suite
Restore runtime type checks for dynamic to class conversions

Note that this will generate exceptions when the value "undefined" is
assigned to a class (since undefined is actually a class instance). Fix
for that will be forthcoming.
Fix additional places using empty string in place of "null"
Remove "TODOs" that have been resolved
Remove parallel restriction from playc_tests Makefile
Add separate BuiltinType for the ActionScript "*" type
Merge remote-tracking branch 'origin/master' into cbroglie-undefined-support
Check if object is enumerable before for/for each

Previously we were checking for null/undefined, but this didn't address
the cases where a dynamic object could hold the value of a primitive.
Fix IsNullOrUndefined logic

The function was mistakenly returning true for the boolean false value.
Also adding IsUndefined as another utility function (to encapsulate the
Object.ReferenceEquals logic).
Support returning undefined from ExpandoObject
Fix spelling error
Merge remote-tracking branch 'origin/master' into cbroglie-undefined-support

Conflicts:
	mcs/class/PlayScript.Dynamic_aot/PlayScript.Dynamic_aot-net.csproj
Make Convert<double>.FromObject return NaN for undefined

Returns NaN for other numeric types as well if the value is undefined
Merge remote-tracking branch 'origin/master' into cbroglie-undefined-support