refactor height filter to appease cppcheck & MSVC (#473)

refactor height filter to appease cppcheck & MSVC (#473)

* refactor heightgrid to appease cppcheck.

With newer versions (somwhere after 1.82) of cppcheck analyzing
height.cc took an excessive amount of time.
By making these variables private static class members instead of
member function static variables we avoid the cppcheck issues.

* tweak height to work around MSVC 2017 error.

and hopefully MSVC 2015 error as well.

* don't include cstdint within class definition.

It can lead to compile failures.  This was done in heightgrid.h,
but the include guards in cstdint hid the error.