Add '--enable-wtmp' option to configure script to let users easily enable WTMP
log support.

If '--enable-wtmp' was given, check if 'utmp.h' is available on the system and
bail out if header file could not be found.
--
 configure.ac |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)
diff --git a/configure.ac b/configure.ac
index af57577..3706eb4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -137,6 +137,12 @@ AC_ARG_ENABLE(iproute2,
    AC_DEFINE(CONFIG_FEATURE_IPROUTE, 1, [enable iproute2 support])   
 )
 
+AC_ARG_ENABLE(wtmp,
+   [  --enable-wtmp           Enable WTMP support (--log-wtmp)],
+   [LOG_WTMP="$enableval"],
+   [LOG_WTMP="no"]
+)
+
 AC_ARG_ENABLE(strict,
    [  --enable-strict         Enable strict compiler warnings (debugging option)],
    [STRICT="$enableval"],
@@ -705,4 +711,13 @@ if test "$PASSWORD_SAVE" = "yes"; then
    AC_DEFINE(ENABLE_PASSWORD_SAVE, 1, [Allow --askpass and --auth-user-pass passwords to be read from a file])
 fi
 
+dnl enable wtmp logging
+if test "$LOG_WTMP" = "yes"; then
+
+  AC_CHECK_HEADER(utmp.h,
+  	[AC_DEFINE(ENABLE_WTMP, 1, [Enable wtmp logging support])],
+ 	[AC_MSG_ERROR([WTMP headers not found])]
+  )
+fi
+
 AC_OUTPUT(Makefile openvpn.spec)