scoutfs: add tracepoint support with bloom example

Add the intrastucture for tracepoints.  We include an example user that
traces bloom filter hits and misses.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile

@@ -1,4 +1,6 @@
 obj-$(CONFIG_SCOUTFS_FS) := scoutfs.o
+
+CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
  
 scoutfs-y += block.o bloom.o chunk.o crc.o dir.o filerw.o inode.o manifest.o \
-	     msg.o ring.o segment.o skip.o super.o
+	     msg.o ring.o scoutfs_trace.o segment.o skip.o super.o