Eliminate unnecesssary _Dynamic_bounds_casts

[dtarditi]

This is related to #3: there are a number of places where a dynamic bounds cast have been inserted to suppress compiler warning messages. A number of them were because the compiler gives warnings when strings with declared bounds are passed to arguments with default bounds of count(0). We should eliminate these once the compiler is smarter.

[ppashakhanloo]

After addressing 0 <= any unsigned integer, the following _Dynamic_bounds_casts can be removed since the compiler can prove them:
lines 515, 670, 673, 285, 527, 1589, 1650, 320, 437, 437, 468, and 469.

Moreover, in line 469, the first argument is actually wrong and should be changed to _Ptr<JSON_Value>.