get rid of version checks

version checks don't work at all on kernels with backported bpf bits
they also fail when /usr/include/linux/bpf.h doesn't match loaded
kernel.
Fix these issues by embedding bpf.h into libbcc.so and force load it
in clang, so we can remove all version checks and rely on verifier
complaining on unknown function call.
Later patch can make verifier errors less cryptic by converting
'unknown call 12' to strings.

while at it update bpf.h to the latest.
Signed-off-by: Alexei Starovoitov <ast@fb.com>

Bug fix around USDT argument handling for constants

For USDT arguments of the form "-4@$-1", the parsing logic would fail
because it didn't expect the second number (the actual value of the
USDT argument as a constant) to be negative. This is now fixed.

IPv6 strings with an inet6_ntoa

Replaced `which --skip-alias` with `ProcUtils.which`

Support for global variable arguments in USDT probes

Lua Tools for BCC

Percpu support