Fix warnings in PlayScript.Dynamic_aot-net project and treat them as errors
Override TextEvent.text implementation to fix warning
Hide inherited RESIZE member to fix warning
Fix warnings by only declaring variables when they're used
Treat warnings as erros in Mono.Optimization
Disable unused variable warning for debug only variable
Treat warnings as errors in mcs project
Set pscorlib_aot-net_monomac to treat warnings as errors
Treat warnings as errors when building mcs release
Don't warn about these fields being assigned and never used
Don't warn about CS019 in pscorlib

The compiler issues a level-three warning, when you declare and assign
a variable, but do not use it. General sentiment is that they're benign,
so let's not worry about them in pscorlib.
Fix warning in Texture.cs
Fix warnings in File.play
Set pscorlib_aot-monodroid to treat warnings as errors and ignore warning CS0219
Set PlayScript.Dynamic_aot-monotouch to treat warnings as errors
Ignore warning CS0618 in PlayScript.Dynamic_aot-monodroid
Treat warnings as errors in PlayScript.Dynamic_aot-monodroid
Bump assembly TargetFramework version to 4.5
Merge pull request #248 from playscript/fix-warnings

Fix warnings on mcs solution and set projects to treat warnings as errors.