Watcom: Detect compiler target architecture and platform

In CMakePlatformId.h.in, fill ARCHITECTURE_ID and PLATFORM_ID for Open
Watcom.
Watcom: Introduce OpenWatcom compiler id and fix compiler version

Distinguish "Open Watcom" from old "Watcom" by introducing a new
"OpenWatcom" compiler id.  The __WATCOMC__ format is "VVRP" for Watcom
and "VVRP + 1100" for Open Watcom.
Watcom: Enable 'WMake Makefiles' generator on Linux
Merge topic 'watcom-updates' into next

64c2342a Watcom: Enable 'WMake Makefiles' generator on Linux
5d9aa66c Watcom: Introduce OpenWatcom compiler id and fix compiler version
9292d3b8 Watcom: Detect compiler target architecture and platform