libperf: Add perf_evlist__init() function

libperf: Add perf_evlist__init() function

Add the perf_evlist__init() function to initialize a perf_evlist struct.

Committer testing:

Fix a change in init ordering that was causing this backtrace:

  (gdb) run stat sleep 1
  Starting program: /root/bin/perf stat sleep 1
  Program received signal SIGSEGV, Segmentation fault.
  0x00000000004f6b55 in __perf_evlist__propagate_maps (evlist=0xbb34c0, evsel=0x0) at util/evlist.c:161
  161		if (!evsel->own_cpus || evlist->has_user_cpus) {
  Missing separate debuginfos, use: dnf debuginfo-install bzip2-libs-1.0.6-29.fc30.x86_64 elfutils-libelf-0.176-3.fc30.x86_64 elfutils-libs-0.176-3.fc30.x86_64 glib2-2.60.4-1.fc30.x86_64 libbabeltrace-1.5.6-2.fc30.x86_64 libgcc-9.1.1-1.fc30.x86_64 libunwind-1.3.1-2.fc30.x86_64 libuuid-2.33.2-1.fc30.x86_64 libxcrypt-4.4.6-2.fc30.x86_64 libzstd-1.4.0-1.fc30.x86_64 numactl-libs-2.0.12-2.fc30.x86_64 pcre-8.43-2.fc30.x86_64 perl-libs-5.28.2-436.fc30.x86_64 popt-1.16-17.fc30.x86_64 python2-libs-2.7.16-2.fc30.x86_64 slang-2.3.2-5.fc30.x86_64 xz-libs-5.2.4-5.fc30.x86_64 zlib-1.2.11-15.fc30.x86_64
  (gdb) bt
  #0  0x00000000004f6b55 in __perf_evlist__propagate_maps (evlist=0xbb34c0, evsel=0x0) at util/evlist.c:161
  #1  0x00000000004f6c7a in perf_evlist__propagate_maps (evlist=0xbb34c0) at util/evlist.c:178
  #2  0x00000000004f955e in perf_evlist__set_maps (evlist=0xbb34c0, cpus=0x0, threads=0x0) at util/evlist.c:1128
  #3  0x00000000004f66f8 in evlist__init (evlist=0xbb34c0, cpus=0x0, threads=0x0) at util/evlist.c:52
  #4  0x00000000004f6790 in evlist__new () at util/evlist.c:64
  #5  0x0000000000456071 in cmd_stat (argc=3, argv=0x7fffffffd670) at builtin-stat.c:1705
  #6  0x00000000004dd0fa in run_builtin (p=0xa21e00 <commands+288>, argc=3, argv=0x7fffffffd670) at perf.c:304
  #7  0x00000000004dd367 in handle_internal_command (argc=3, argv=0x7fffffffd670) at perf.c:356
  #8  0x00000000004dd4ae in run_argv (argcp=0x7fffffffd4cc, argv=0x7fffffffd4c0) at perf.c:400
  #9  0x00000000004dd81a in main (argc=3, argv=0x7fffffffd670) at perf.c:522
  (gdb) bt

So move the initialization of the core evlist (calling
perf_evlist__init()) to before perf_evlist__set_maps() in
evlist__init().

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190721112506.12306-39-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>