* harbour/src/rtl/gtos2/Makefile
* harbour/config/os2/watcom.mk
* disable -s in GTOS2 OpenWatcom builds using HB_CSTACK_CHECK variable.
This is workaround for wrong code generated by OpenWatcom <= 1.8
when -s switch is used for functions calling APIENTRY16 functions.
Such code executed from non main thread causes GPF.