Add module level SkipLocalsInit

[lahma]

Let's extract some free perf with the magic attribute. Fluid doesn't expect specific initialization and usages should be safe. Same thing is used in Parlot, Esprima and Jint.

Fluid.Benchmarks.FluidBenchmarks

Diff	Method	Toolchain	Mean	Error	Allocated
Old	Parse	Default	4.455 μs	0.0235 μs	2.68 KB
New		Default	4.345 μs (-2%)	0.0164 μs	2.68 KB (0%)
Old	ParseBig	Default	23.970 μs	0.1198 μs	11.61 KB
New		Default	23.470 μs (-2%)	0.0663 μs	11.61 KB (0%)
Old	Render	Default	189.348 μs	0.6141 μs	95.86 KB
New		Default	191.471 μs (+1%)	0.7625 μs	95.86 KB (0%)
Old	ParseAndRender	Default	200.195 μs	0.4416 μs	99.01 KB
New		Default	197.654 μs (-1%)	0.5037 μs	99.01 KB (0%)