fix zh-cn Doxygen generation for Travis CI

Localize documents to simplified Chinese

Fixes for GCC with -pedantic

tutorial.cpp: fix insitu parsing (closes #273)

The insitu parsing example in the tutorial is using a local char
buffer inside a nested scope.  After leaving the scope, the
resulting Document object still references this (now invalid)
memory locations.

Some compilers reuse this space on the stack for other local
variables later in the function, corrupting the original document.

Drop the local scope to extend the lifetime of the buffer.

document.h: include <string>, iff RAPIDJSON_HAS_STDSTRING==1

Reported-by: Janusz Chorko (@yachoor)
See: https://github.com/miloyip/rapidjson/commit/c1c9ba7c#commitcomment-10434694

Check libstdc++ version to decide if enable rvalue ref support.

.travis.yml: disable SSE4.2 on 32-bit (closes #266)

Exclude intermediate files from install of in-source build. (Issue #259)

Fix VS2012 compilation fail in stringbuffertest

Skip running perftest on CI debug builds (Appveyer; Travis)

GenericValue::AddMember<T>: add missing overload (closes #254)

RapidJSON is C++, need to set CMAKE_CXX_FLAGS instead
of CMAKE_C_FLAGS when configuring the build environment.

(Accidentally dropped in 40c03114)