recent runtime changes

[Martin Hunt <hunt at redhat dot com>]

I've been busy updating the runtime.  Here's a quick status.

The tagged data proposal I sent a few weeks ago has been postponed until
a later release.  Instead I reworked the map code to support more than 2
keys, which I had not planned to do until 2.0.

New map code - 
* up to five keys
* keys are now strings or int64s instead of longs
* histograms (log and linear) work
* The new code uses templates similar to what the old dtr prototype did,
only easier to use and with more features.
* No kmallocs at all, but you must declare a maximum string length for
maps. Default is 256.

For examples, see src/runtime/probes.  I have tested them all on x86_64
and i386.

New userspace test code for the maps is checked in and a start on more
general userspace tests.

Next:
1. relayfs vs netlink tests. I don't see an easy way to detect when
relayfs thinks it has lost data, so I'll have to transmit some pattern
and see if data is missing.

2. print.c changes. Use an atomic counter instead of a timestamp for
relayfs packets. Have stpd mix the per-cpu files back together.

3. Enhancements for String code. Partially done already.

4. Use new String code to clean up stack.c, sym.c and current.c
They are currently a work-in-progress and not complete.

5. Document.  The online documentation is currently extremely out-of-
date.  

6. Aggregations? Currently we have them as part of maps only.

Martin