Generic Monitoring Framework with DTrace patch

Hi,

I've have attached a patch along with two new files.This patch should
reflect what we discussed at the Summit. Please let me know if I miss
anything.

There are a few potential/known issues which I need help from the gurus.

1) The current logic in src/backend/Makefile will only work for Solaris
versions with DTrace, and Peter has offered to help fix this one.

2) Currently an environment variable called DTRACE_DATA_MODEL is used in
src/backend/Makefile to tell the dtrace command whether to generate a 32
or 64 bit binary. This may not be a reliable approach since a user can
forget to set this variable. Perhaps adding a flag like DTRACEFLAGS to
the configure script is a better approach. Thoughts?

3) When using --enable-depend, "gmake clean" removes all *.d files,
including the DTrace probe definition file which also has a .d
extension. I tried to to use a different extension but the dtrace tool
didn't like that. Since we only plan to have one probe definition file
(pgsqlprobes.d) and one provider called "postgresql", I think
src/Makefile.global.in can be changed to not remove this file. Is this
acceptable or is there a better solution?

I have created several DTrace scripts and uploaded them to
http://pgfoundry.org/projects/dtrace/

Many thanks to Gavin and Tom for their help with creating and inserting
the current set of probes, and Peter for his help with the config files.

Regards,
-Robert