Could MSGBUF_SIZE be made a loader tunable?

[perryh at pluto.rain.com]

Would there be some fundamental problem in changing MSGBUF_SIZE
from a compiled-in constant to a tunable that could be set at the
loader prompt?  (I'm _not_ suggesting that it be adjustable while
the system is running.)

The upside would be that, if someone needed a larger buffer
temporarily to accommodate trace data from a mechanism such as
kern.geom.debugflags, the size could be adjusted without having
to rebuild the kernel.

I didn't see any obvious downside from examining the 8.1-RELEASE
code, but I could certainly have overlooked some subtle (or even
blatant) reason why this would be a Bad Idea.