Fix Win32 Makefile generation

Fix Win32 Makefile generation

Change 200cbd6 (mistakenly reverted by 1487aac but then re-applied by 2f30d0d)
was first assimilated by EU-MM in 6.50, but it was assimilated wrongly: the tabs
were converted to spaces. Somehow that didn't find its way back into the core
when 6.50 was integrated (76467b2), but did when 6.52 was integrated (5bdf71c).
I've only recently noticed it when I found that building blead with dmake fell
over in the Win32CORE build with the error:

dmake:  makefile:  line 454:  Error: -- An AUGMAKE meta target must not be mixed
with non AUGMAKE meta targets, offending target [.manifest]

Restoring the tabs fixes this, and the build now works with dmake again.