While compiling 3.6.0pre2, I went on the following issue:

Compiling winbindd/idmap_tdb2.c
winbindd/idmap_tdb2.c: In function 'idmap_tdb2_open_db':
winbindd/idmap_tdb2.c:118:50: error: 'O_RDWR' undeclared (first use in this function)
winbindd/idmap_tdb2.c:118:50: note: each undeclared identifier is reported only once for each function it appears in
winbindd/idmap_tdb2.c:118:57: error: 'O_CREAT' undeclared (first use in this function)
The following command failed:
gcc -g -Wall -O2 -I. -I/tmp/buildd/samba-3.6.0~pre2/source3 -I/tmp/buildd/samba-3.6.0~pre2/source3/../lib/iniparser/src -Iinclude -I./include  -I. -I. -I./../lib/replace -I./../lib/tevent -I./librpc -I./.. -I../lib/tdb/include -I/usr/include -DHAVE_CONFIG_H  -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Iinclude -I./include -I. -I. -I./../lib/replace -I./../lib/tevent -I./librpc -I./.. -I./../lib/popt -DLDAP_DEPRECATED  -I/tmp/buildd/samba-3.6.0~pre2/source3/lib -I.. -D_SAMBA_BUILD_=3 -D_SAMBA_BUILD_=3 -fPIC -c winbindd/idmap_tdb2.c -o winbindd/idmap_tdb2.o
make[1]: *** [winbindd/idmap_tdb2.o] Error 1
make[1]: Leaving directory `/tmp/buildd/samba-3.6.0~pre2/source3'
make: *** [build-stamp] Error 2

A naive fix was:

--- samba-3.6.0~pre2.orig/source3/winbindd/idmap_tdb2.c
+++ samba-3.6.0~pre2/source3/winbindd/idmap_tdb2.c
@@ -32,6 +32,7 @@
 */
 
 #include "includes.h"
+#include "fcntl.h"
 #include "winbindd.h"
 #include "idmap.h"
 #include "idmap_rw.h"


I find this too simple to be the right solution..:-)