We should include the <cfloat> header file by default #1161
Description
One thing became apparent during the work on #1158 for STRICT_R_HEADERS: a majority of patches / PRs simply require an #include of float.h (or, equivalently, cfloat).
Is there any reason we should not add that to RcppCommon.h?
We already include <limits> which, as I re-learned, only covers integer limits to <cfloat> would make sense.