Implement the historic DIOCGDINFO ioctl for gpart on BSD
partitions. Several utilities still use this interface and require
additional information since gpart was activated than before. This
allows fsck of a UFS partition without having to specify it is UFS,
per historic behavior.
Acutally, replaces NO_INCS with WITHOUT_INCLUDES and make
WITHOUT_TOOLCHAIN imply it instead.

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Fix typo pointed out by avg@ and Joerg Sonnenberger. Add a clarifying
sentence too.

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LIB32 is supported for powerpc64 too. Make the note more general about
64-bit processors.

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Document WITHOUT_USB_EXAMPLES and WITHOUT_TESTS_SUPPORT

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opt_global.h is never needed in SRCS lists.

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No need to list opt_global.h. No need to force ALTQ here, since that's
not the normal default for the system and nothing else forces it on.

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opt_global.h is included automatically in the build. No need to
explicitly include it in these places.

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These delays aren't needed. Elimate them. They should be on the order
of a few cycles at most, not 10us. They make it impossible to
implement half-duplex protocols that are faster than about 1KHz.

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