Unit Test: Parsing "0e100" in full precision mode causes UB

Fix strtod

until I know what the normal-precision algorithm really does...

Some more need to be fixed.

=D

Do not use an approximation to do this. Instead check if the result is Inf.

If the buffer only contains zeros, return 0.

MSVC: Autodetect RAPIDJSON_HAS_CXX11_NOEXCEPT, RAPIDJSON_HAS_CXX11_TYPETRAITS

Avoid `MissingProperty` Error from `SchemaValidator` when a none-zero length value is given as `default` for the property

again, in relation to solving issue #784, use `SizeType`-typed variable to indicate a none-zero length string has been given in the schema as default value for the json property; added an unittest `Object_Required_PassWithDefault`

in relation to solving issue #784, this commit enables the schema to recognise the "default" property, and avoids a missing property error when a default is given in the schema

Prevent int underflow when parsing exponents

When parsing negative exponents, the current implementation takes
precautions for |exp| to not underflow int.

But that is not sufficient: later on [1], |exp + expFrac| is also
stored to an int - so we must ensure that the sum stays within int
representable values.

Update the exp clamping logic to take expFrac into account.

[1] https://github.com/Tencent/rapidjson/blob/master/include/rapidjson/reader.h#L1690

Merge

Added const for Reader methods

Fix compilation on windows with clang