Add support for Linux Containers, fixes #202.

Patch by bug reporter.

src/librc/librc.c

@@ -233,6 +233,8 @@ rc_sys(void)
 		return RC_SYS_VSERVER;
 	else if (exists("/proc/vz/veinfo") && !exists("/proc/vz/version"))
 		return RC_SYS_OPENVZ;
+	else if (file_regex("/proc/self/cgroup", ":/.+$"))
+		return RC_SYS_LXC;
 	else if (file_regex("/proc/self/status",
 		"envID:[[:space:]]*[1-9]"))
 		return RC_SYS_OPENVZ; /* old test */

src/librc/rc.h.in

@@ -268,6 +268,7 @@ bool rc_service_daemons_crashed(const char *);
  * Some services cannot work in these systems, or we do something else. */
 #define RC_SYS_JAIL    "JAIL"
 #define RC_SYS_OPENVZ  "OPENVZ"
+#define RC_SYS_LXC     "LXC"
 #define RC_SYS_PREFIX  "PREFIX"
 #define RC_SYS_UML     "UML"
 #define RC_SYS_VSERVER "VSERVER"