Also skip io/eintr.t on MidnightBSD
Amend 'new perldelta' advice for Win32

test_porting is supported as target for both gcc and VC++ builds

win32/Makefile since 247c55c00b852ec1da004aff2c0e2d4b07af55ab

win32/makefile.mk since 106cf76e392294bc0fe10a3efa306d011f3b2e3c