Until now it depended on the parameter-order whether
integers and floats were compared as integers or floats.

Appart from being not logical, this might even have meant that
the provided “order” was in fact not that. (not sure here, but I
like to be carefull)

Fix compilation of json_unit with GCC 5

Addressing:
```
+ make json_unit
g++ -std=c++11  -Wall -Wextra -pedantic -Weffc++ -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wmissing-declarations -Wmissing-include-dirs -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wsign-conversion -Wsign-promo -Wstrict-overflow=5 -Wswitch -Wundef -Wno-unused -Wnon-virtual-dtor -Wreorder -Wdeprecated -Wfloat-equal  -I src -I test -Dprivate=public test/unit.cpp  -o json_unit
In file included from test/catch.hpp:65:0,
                 from test/unit.cpp:11:
/usr/include/c++/5.0.0/sstream:300:7: error: 'struct std::__cxx11::basic_stringbuf<_CharT, _Traits, _Alloc>::__xfer_bufptrs' redeclared with different access
       struct __xfer_bufptrs
```