Added basic detection of `noexcept` support for some compilers, added
corresponding RAPIDJSON_NOEXCEPT annotations to
 * non-allocating constructors
 * (move) assignment
 * Swap

Directly allows temporary GenericValues as parameters:
  v.AddMember("foo", Value(s.c_str(),alloc), alloc);

See https://code.google.com/p/googletest/wiki/FAQ#Why_should_not_test_case_names_and_test_names_contain_underscore

When C++11 is enabled, several algorithms will fail, if GenericValue is
neither copyable, nor movable.

Cherry-picked from 8005b55.

Fix comparison operator ambiguities between Value/Document

Before applying the simplifications in ed282b81, the SFINAE check for the
GenericValue(bool) constructor has been broken in MSVC 2005. Add a static
assert as a safe-guard against future reappearance of this problem.

This finally fixes #113.

In order to match GenericValue and its derived classes for the
SFINAE-implementation of some of the operators/functions, this
meta-function matches all types equal to or derived from a given
class.  See std::is_base_of<B,D> available in C++11.

Define RAPIDJSON_HAS_CXX_TYPETRAITS to use the C++11 implementation.

Some (older) compilers have problems with compile-time constants.
This commit simplifies the implementation of the helper classes
in order to improve compiler support, especially be removing the
need of partial template specialisation.

No functional changes.

Prepare equalto_operator tests to test comparisons between
 * GenericValue and GenericDocument
 * GenericValue with different SourceAllocator types

Both combinations currently fail due to ambiguities with the
templated operators on several compilers.

Replace tmpname() by mkstemp() on non-MSVC compilers

Three new APIs are added for JSON object type.

Fix `RAPIDJSON_HAS_STDSTRING is not defined` compilation warning

Fixes #118

Use local typedef to invoke GenericMember's destructor

As reported in #113, recent versions of Clang complain about
ambiguous overloads for some comparison operator instantiations,
especially if the deduced template type is a GenericValue.

Add an explicit, non-templated version for now (which is a better
match).

This only solves part of the problem, as comparisons between
  * GenericValue & GenericDocument
  * GenericValue with different SourceAllocator types
will still cause ambiguities.

GenericMemberIterator: fix comparisons/differences for mixed-constness expressions

Parsing optimization

Do unaligned non-SIMD matching first, and then SIMD matching later.
Also add a fast path for no skipping.

GenericValue: add optional support for std::string