Only truncate the dirhash state when directory truncation succeeds.

From FreeBSD commit f1c05bd42b549bdfbd6d418c0bb9c947293d9837
ok pedro@
Switch /usr/bin/cpp to use tradcpp.

ok drahn@
Complete list of include path options (and sort).

ok drahn@
-U__GNUC__ doesn't need special handling.

ok drahn@
tradcpp doesn't have the -arch option.

ok drahn@
s/openbsd.org/bitrig.org/ in some manual pages.
Adapt afterboot.8 for Bitrig.
Remove gcc-local(1); Bitrig doesn't use gcc.
trim ld.so code for unsupported architectures

ok natano@ patrick@
Use pax(1) to build the file system for bsd.rd.

ok pedro@ (for amd64)
ok patrick@ (for armv7)