Implemented PERF_RECORD_COMPRESSED event, related data types, header
feature and functions to write, read and print feature attributes from
the trace header section.

comp_mmap_len preserves the size of mmaped kernel buffer that was used
during collection. comp_mmap_len size is used on loading stage as the
size of decomp buffer for decompression of COMPRESSED events content.

Committer notes:

Fixed up conflict with BPF_PROG_INFO and BTF_BTF header features.
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/ebbaf031-8dda-3864-ebc6-7922d43ee515@linux.intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>