Compile failure on Mac platform

[cschol]

On Mac you need an explicit

#include <array>

Compiler output:

x86_64-apple-darwin17-clang++  -std=c++11 -stdlib=libc++   -fPIC -I/home/cschol/src/Rack-SDK/Rack-SDK/include -I/home/cschol/src/Rack-SDK/Rack-SDK/dep/include -MMD -MP -g -O3 -march=nocona -funsafe-math-optimizations -Wall -Wextra -Wno-unused-parameter -DARCH_MAC -mmacosx-version-min=10.7  -c -o build/src/Scal
eQuantiser.cpp.o src/ScaleQuantiser.cpp
src/PolyVolt.cpp:125:27: error: implicit instantiation of undefined template 'std::__1::array<Quantiser, 16>'                                                                                                                                                                                                         
        std::array<Quantiser,16> quantisers;
                                 ^                                                                                                                                                                                                                                                                                    
/home/cschol/src/osxcross/target/bin/../SDK/MacOSX10.13.sdk/usr/include/c++/v1/__tuple:223:64: note: template is declared here
template <class _Tp, size_t _Size> struct _LIBCPP_TEMPLATE_VIS array;                                                                                                                                                                                                                                                 
                                                               ^
src/PolyVolt.cpp:126:23: error: implicit instantiation of undefined template 'std::__1::array<float, 16>'                                                                                                                                                                                                             
        std::array<float,16> inVolts;

[cschol]

Fixed.