tools lib traceevent: Add install_headers target

Adding install_headers target to install all headers
under 'include/traceevent' path, like:

  $ make DESTDIR=/tmp/krava prefix=/usr install_headers
  $ find /tmp/krava/ -type f
  /tmp/krava/usr/include/traceevent/kbuffer.h
  /tmp/krava/usr/include/traceevent/event-utils.h
  /tmp/krava/usr/include/traceevent/event-parse.h
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/n/tip-if70lj3zhdc3csdqm5webjvc@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/Makefile

@@ -240,7 +240,7 @@ define do_install
 	if [ ! -d '$(DESTDIR_SQ)$2' ]; then		\
 		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$2';	\
 	fi;						\
-	$(INSTALL) $1 '$(DESTDIR_SQ)$2'
+	$(INSTALL) $(if $3,-m $3,) $1 '$(DESTDIR_SQ)$2'
 endef
 
 define do_install_plugins
@@ -264,6 +264,12 @@ install_plugins: $(PLUGINS)
 	$(call QUIET_INSTALL, trace_plugins) \
 		$(call do_install_plugins, $(PLUGINS))
 
+install_headers:
+	$(call QUIET_INSTALL, headers) \
+		$(call do_install,event-parse.h,$(prefix)/include/traceevent,644); \
+		$(call do_install,event-utils.h,$(prefix)/include/traceevent,644); \
+		$(call do_install,kbuffer.h,$(prefix)/include/traceevent,644)
+
 install: install_lib
 
 clean: