tools/trace accepts abspath arguments to -I (and some doc tweaks)

Fix ucalls

fixes #962 - fix lambda on both py2 and py3

gethostlatency: Filter by process ID

u* tools: Gracefully handle missing probes

When the target process is missing the required USDT probes, it can
be a simple mistake (e.g. attaching a script as Java to a Python
process), or a runtime that is not instrumented with the required
probes. Attempt to gracefully handle the error and print a helpful
message instructing the user why the error might have occurred.

```
$ uthreads -l java $(pidof python)
Error attaching USDT probes: the specified pid might not contain
the given language's runtime, or the runtime was not built with the
required USDT probes. Look for a configure flag similar to
--with-dtrace or --enable-dtrace. To check which probes are present
in the process, use the tplist tool.
```

u* tools: PHP support

ugc: Add -M for minimum time and -F for text filtering

See: https://www.python.org/dev/peps/pep-3113/

$ ucalls
  File "./ucalls", line 239
    data = map(lambda (k, v): (k.clazz + "." + k.method,
                      ^
SyntaxError: invalid syntax

See: https://www.python.org/dev/peps/pep-3113/

On python3 map returns a generator instead of a list. This fixes the
following error:

Traceback (most recent call last):
  File "./ucalls", line 280, in <module>
    data = get_data()   # [(function, (num calls, latency in ns))]
  File "./ucalls", line 255, in get_data
    data.extend(syscalls)
AttributeError: 'map' object has no attribute 'extend'

Fix uobjnew and ustat on python3

Debian jessie .deb build config and automated test fixes.

$ ./ustat
  File "./ustat", line 242
    counts = sorted(counts.items(), key=lambda (_, v):
                                               ^
SyntaxError: invalid syntax

$ ./uobjnew
  File "./uobjnew", line 150
    data = sorted(data.items(), key=lambda (k, v): v.num_allocs)
                                           ^
SyntaxError: invalid syntax

This fixes a TypeError in python 3, e.g, when executing uobjnew

Traceback (most recent call last):
  File "./uobjnew", line 134, in <module>
    bpf = BPF(text=program, usdt_contexts=[usdt])
  File "/usr/lib/python3.5/site-packages/bcc/__init__.py", line 224, in __init__
    text = usdt_text + text
TypeError: can't concat bytes to str

Use fast compression in test deb builds

Builds on GCE/ubuntu image were taking a long time due to combination of
disk speed/single core, and the default dpkg-deb compression level
(-z9). The dpkg-deb alone step was taking up to 5 minutes. Reduce to ~1
minute by forcing -z1. Unfortunately, it was not obvious how to capture
the option in debuild command, so this is a bit hacky.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Fixes for LLVM4+, python3

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

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

In python3, output needs to be converted from ascii to str before the
"error_msg in str" test will succeed. This change should be backwards
compatible with python2.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Diff generated by clang-format
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Recent llvm changed the calling convention of setInvocation, breaking
3.9/4.0 compatibility. This new approach works for both.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

Without marking as nounwind, recent llvm started generating .eh_frame
section, which is invalid for bpf target jit.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

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

Use PID to resolve path of target libraries

trace: fix for python3

snapcraft: add in some missing tools from the snapcraft apps list

tplist: don't fail if no verbosity is supplied

update tools pic

Initialise the verbosity argument to 0, so that when no verbosity is
provided we don't fail with

$ tplist
kvmmmu:kvm_mmu_pagetable_walk
unorderable types: NoneType() > int()

Minor debian/control file updates
Added Debian - Source section to INSTALL.md