perf tests: Fix build on older systems where 'signal' is reserved

fixing the following problems, for instance, on RHEL6.7:

    CC       /tmp/build/perf/tests/bp_signal.o
  cc1: warnings being treated as errors
  tests/bp_signal.c: In function ‘__event’:
  tests/bp_signal.c:106: error: declaration of ‘signal’ shadows a global declaration
  /usr/include/signal.h:101: error: shadowed declaration is here
  tests/bp_signal.c: In function ‘bp_event’:
  tests/bp_signal.c:144: error: declaration of ‘signal’ shadows a global declaration
  /usr/include/signal.h:101: error: shadowed declaration is here
  tests/bp_signal.c: In function ‘wp_event’:
  tests/bp_signal.c:149: error: declaration of ‘signal’ shadows a global declaration
  /usr/include/signal.h:101: error: shadowed declaration is here
  mv: cannot stat `/tmp/build/perf/tests/.bp_signal.o.tmp': No such file or directory
  make[3]: *** [/tmp/build/perf/tests/bp_signal.o] Error 1
  make[2]: *** [tests] Error 2
  make[1]: *** [/tmp/build/perf/perf-in.o] Error 2
  make[1]: *** Waiting for unfinished jobs....

Reported-by: Vinson Lee <vlee@freedesktop.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: He Kuang <hekuang@huawei.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: pi3orama@163.com
Fixes: 8fd34e1cce18 ("perf test: Improve bp_signal")
Link: http://lkml.kernel.org/n/tip-wlpx6tik1b0jirlkw64bv400@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/bp_signal.c

@@ -103,7 +103,7 @@ static void sig_handler(int signum __maybe_unused,
 	}
 }
 
-static int __event(bool is_x, void *addr, int signal)
+static int __event(bool is_x, void *addr, int sig)
 {
 	struct perf_event_attr pe;
 	int fd;
@@ -133,7 +133,7 @@ static int __event(bool is_x, void *addr, int signal)
 	}
 
 	fcntl(fd, F_SETFL, O_RDWR|O_NONBLOCK|O_ASYNC);
-	fcntl(fd, F_SETSIG, signal);
+	fcntl(fd, F_SETSIG, sig);
 	fcntl(fd, F_SETOWN, getpid());
 
 	ioctl(fd, PERF_EVENT_IOC_RESET, 0);
@@ -141,14 +141,14 @@ static int __event(bool is_x, void *addr, int signal)
 	return fd;
 }
 
-static int bp_event(void *addr, int signal)
+static int bp_event(void *addr, int sig)
 {
-	return __event(true, addr, signal);
+	return __event(true, addr, sig);
 }
 
-static int wp_event(void *addr, int signal)
+static int wp_event(void *addr, int sig)
 {
-	return __event(false, addr, signal);
+	return __event(false, addr, sig);
 }
 
 static long long bp_count(int fd)