FreeBSD_HEAD_i386 - Build #1558 - Fixed

FreeBSD_HEAD_i386 - Build #1558 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1558/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1558/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/1558/console

Change summaries:

290224 by imp:
The error classification from lower layers is a poor indicator of
whether an error is recoverable. Always re-dirty the buffer on errors
from write requests. The invalidation we used to do for errors not EIO
doesn't need to be done for a device that's really gone, since that's
done in a different path.

Reviewed by: mckusick_at_, kib_at_

290223 by imp:
Rather than using the #define for path names, indirect through a char *
variable that could change for different executable types detected.

290222 by imp:
Move all the paths into a new path.h to centralize them.

290221 by jhibbits:
Print unsigned memory sizes, to handle >2GB RAM on 32-bit powerpc.

Sponsored by:	Alex Perez/Intertial Computing

290220 by bdrewery:
Don't hide stderr when checking ${CC} --version.

This can have important debugging information such as 'cc: not found' or
'ccache: error: Could not find compiler "cc" in PATH'.

MFC after:	2 weeks
Sponsored by:	EMC / Isilon Storage Division