Remove all VMS-specific code from the library. The exception is the VMS
floating-point tests since those are special as VMS floats are odd.
Those files will be considered separately.
Fixes HDFFV-9495
Tested on: h5committest
Eliminates gcc warnings due to -Wunsuffixed-float-constants.
- Adds 'F' suffixes for most float constants.
- A few constants MUST be of type double. These now receive the long
double L suffix and are then cast to double. I do this via a new
H5_DOUBLE() macro which was added to H5private.h.
- Additionally, some 1.8-specific float suffixes were added.
Fixes: HDFFV-9148
Tested on: h5committest
