FreeBSD_HEAD - Build #3143 - Fixed

FreeBSD_HEAD - Build #3143 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3143/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3143/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3143/console

Change summaries:

287263 by imp:
Comment out cleaning files, since it cleans too much.

287262 by imp:
Remove .WAIT hacks and put in specific dependencies.

287260 by imp:
Add missing ofw_machdep.h. Make x86 ofw_machdep.h work pc98 too.
This allows the owc module to compile on pc98 and seems preferable to
adding another special case in the build system.

287259 by pfg:
Add underscores to attributes when checking for __has_attribute.

This is a good practice to avoid confusion with allowed macros.

Suggested by:	jilles