Fixes for LLVM 4.0 and python3

Avoid conflicting [no]inline attributes in function annotation. This was
probably always there but now 4.0 is treating this as an error.
Also, explicitly inline several functions in helpers.h.

Turn off unwind tables in the flags passed to clang. This was generating
calls to the elf relocator, which doesn't work for the BPF target. It is
unclear which change in LLVM 4.0 altered this behavior.

On python3, handle byte strings in the usual way for supporting
backwards compatibility.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Update [virtual_]bpf.h to 4.10

Only the virtual_bpf.h should point to the installed kernel headers.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

As is occassionally necessary, we need to update the compat header
files for new kernels. This picks up the bpf.h from 4.10rc1.

Fixes: #877
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Fix variable names in exceptions

add cpuunclaimed

Add snapcraft script to package up bcc as a snap

Don't close extern table when a module destructs

add bpf_obj_pin/bpf_obj_get to pin/get bpf objects

support macro in call arguments

trace: -L, -t, -T switches

USDT tools for higher level languages

The `-t` switch for specifying a thread id has been renamed
to `-L`. The `-T` switch specifies that a time column should
be provided, whereas the `-t` switch requests a relative
timestamp (from the beginning of the trace). This is more
consistent with other tools, and lets the user choose the
desired format for the time column, if any.

When C allocations are traced, attach the `malloc`
uprobe only to the requested process -- otherwise, we
get allocation information from the entire system.

If the process in question doesn't have the USDT probes we
expect, handle the failure gracefully. After all, it could
be a binary compiled without USDT support, the pid could be
recycled to some other application, or -- the process name
could match, but by accident, and really belong to some
other runtime.

The /proc/PID/cmdline file has \0 for spaces in the command
line, and there may be trailing \0 characters as well.
Replace them all with spaces.

This tool traces method executions and prints out messages
with a nesting depth indicator that allows relatively easy
visualization of program flow. To reduce overhead, `-C` and
`-M` switches take class and method prefixes to filter the
output by. The filtering takes place in the BPF program, so
the unnecessary data never ends up in user space.

Usage examples:

```
uflow java 185
uflow -M index python 180
uflow -C 'IRB::Irb' ruby 10041
```

This tool gathers statistics (by pid) on method calls,
class loads, garbage collections, thread creations, object
allocations, and exceptions raised and prints them in a
top-like style. Supported languages currently include
Java, Python, Ruby, and Node. Not all languages provide
the necessary probes for all event types.

Usage examples:

```
ustat -C
ustat -l java 1
ustat -l ruby -S objnew
```

Allow callers to obtain the list of active (enabled) USDT
probes from the USDT object, if they need to enable the
uprobes by hand without using the bcc attach support. This
is required when the same uprobe needs to be enabled in
more than one process.