Add filter by cgroup-v2 id

INSTALL.md: add clang-devel as Fedora build dep

To get the cgroup id, you can use the following program to call
name_to_handle_at(), borrowed from
linux/tools/testing/selftests/bpf/cgroup_helpers.c:
```
wget https://gist.githubusercontent.com/alban/4a9aea9636d9fdf11709eddd21df4cc4/raw/f4fc915483a069d6044957e27df091923f95c48b/getcgroupid.c
gcc -Wall -o getcgroupid getcgroupid.c
./getcgroupid /sys/fs/cgroup/unified/
0x100000001
4294967297
```

To test it, I run the tracer in one terminal:
```
./build.sh
sudo ./build-release/src/bpftrace -e 'tracepoint:syscalls:sys_enter_openat /cgroup == 0x100000001/ { printf("%s\n", str(args->filename)); }'
```

And some tests in another terminal:
```
sudo -s
echo $$ > /sys/fs/cgroup/unified/cgroup.procs
cat /dev/null
```

And observe the output of the tracer:
```
Attaching 1 probe...
/etc/ld.so.cache
/lib64/libc.so.6
/usr/lib/locale/locale-archive
/dev/null
^C
```

List clang-devel as a build dependency on Fedora.
Otherwise 'cmake' fails with:

```
CMake Error at CMakeLists.txt:67 (find_package):
  By not providing "FindClang.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Clang", but
  CMake did not find one.

  Could not find a package configuration file provided by "Clang" with any of
  the following names:

    ClangConfig.cmake
    clang-config.cmake

  Add the installation prefix of "Clang" to CMAKE_PREFIX_PATH or set
  "Clang_DIR" to a directory containing one of the above files.  If "Clang"
  provides a separate development package or SDK, be sure it has been
  installed.
```

Remove llvm, llvm-libs since llvm-devel already pulls them in.

fixed some small errors

add fedora installation instructions to readme

update tutorial with kprobe struct args

fixes: https://github.com/iovisor/bpftrace/issues/8

Update README/INSTALL

filename typo

Tools

To get full arguments to pass into Clang for reading kernel headers

cmake: rename gtest external project target

This avoids a conflict in some environments (Arch Linux)

Fixes: #135
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

update more tools to use args

Tracepoint adjust integer types

promote scalar printf args to 64-bits

freeze googletest version

We have googletest as a dependency for our tests. This dependency is
defined by cmake and fetched when we run make, but we were always
fetching master, which means if there is a breaking change upstream our
build will break without notice (which happened recently). To avoid
this, we freeze the googletest version to the last stable, and once
there's a new googletest release we can upgrade it here (making changes
to our code if necessary).

Fixes: https://github.com/iovisor/bpftrace/issues/122

Due to BPF stack alignment restrictions, LLVM might change the size used
to stored printf arguments in the stack, resulting in alignment issues
when formatting and outputting those arguments. To avoid this issue, we
promote every non-array argument to 64-bits, assuring the size used to
store the argument is the same used to dereference it later when calling
printf.

Fixes: https://github.com/iovisor/bpftrace/issues/47

add make install target

enforce infinite rlimit to avoid problems when allocating maps

update tutorial with tracepoint args