When building against linux 3.2, we get this build error:

  building /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/lttng-probe-ext3.o
    CC [M]  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/lttng-probe-ext3.o
  In file included from /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/lttng-events.h:759:0,
                   from /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/define_trace.h:148,
                   from /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/ext3.h:868,
                   from /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/lttng-probe-ext3.c:48:
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h: In function '__event_probe__ext3__page_op':
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:240:1: error: dereferencing pointer to incomplete type
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:240:1: error: dereferencing pointer to incomplete type
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:240:1: error: dereferencing pointer to incomplete type
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h: In function '__event_probe__ext3_invalidatepage':
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:298:1: error: dereferencing pointer to incomplete type
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:298:1: error: dereferencing pointer to incomplete type
  /tmp/nix-build-lttng-modules-2.2.0.drv-0/lttng-modules-2.2.0/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/ext3.h:298:1: error: dereferencing pointer to incomplete type

because a check for existing ext3/*h files in the kernel build tree is skipped
for linux < 3.4. Fix it by extending the ext3_dep_check thing to also be run
when building against linux >= 3.2 (not only linux >= 3.4).

diff -uNr lttng-modules-2.2.0.orig/probes/Makefile lttng-modules-2.2.0/probes/Makefile
--- lttng-modules-2.2.0.orig/probes/Makefile	2013-06-19 03:22:44.000000000 +0200
+++ lttng-modules-2.2.0/probes/Makefile	2013-07-06 13:22:15.902957717 +0200
@@ -59,7 +59,7 @@
 ext3_dep_check = $(wildcard $(ext3_dep))
 ext3 = $(shell \
 	if [ $(VERSION) -ge 3 -a $(PATCHLEVEL) -ge 1 ] ; then \
-		if [ $(VERSION) -ge 3 -a $(PATCHLEVEL) -ge 4 -a \
+		if [ $(VERSION) -ge 3 -a $(PATCHLEVEL) -ge 2 -a \
 			-z "$(ext3_dep_check)" ] ; then \
 			echo "warn" ; \
 			exit ; \