Proposal: Unify printing the function name in panic messages()

[Kirk McKusick]

I have recently gone down several ratholes trying to understand a
panic message which had the wrong function name (prefix ufs1_ instead
of ufs2_).  I can definitely say that it matters to me. And I think
that fixing the problem as Christoph has outlined will be a big
step in the right direction.

John, in your code you cannot expect to match the entire panic
string if it has any % formats in it. So to be useful, you must be
able to work with a constant subset of the string. The addition of
other information such as a function name at the start should not
affect that constant part that you are trying to match.

Though a bit ugly, I do think that the change should use "PANIC"
rather than overloading "panic". First, it lets the feature be
introduced over time rather than requiring that every panic be
changed at once. And, it allows historic panic's to work as expected.

Finally, having it as a macro means that folks can readily and
consistently add file and/or line numbers to panic messages if they
wish to do so.

Summary: I think that this is an excellent idea that will both help
in finding the location of panic errors and also will allow folks
trying to minimize kernel size to do so by cutting out the overhead.

	Kirk McKusick