Copy XENHVM config file from amd64, now that i386+XENHVM works.

sys/i386/conf/XENHVM

@@ -0,0 +1,24 @@
+#
+# XENHVM -- Xen HVM kernel configuration file for FreeBSD/amd64
+#
+# $FreeBSD$
+#
+include		GENERIC
+ident		XENHVM
+
+makeoptions	MODULES_OVERRIDE=""
+
+#
+# Adaptive locks rely on a lock-free pointer read to determine the run state
+# of the thread holding a lock when under contention; under a virtualisation
+# system, the thread run state may not accurately reflect whether the thread
+# (or rather its host VCPU) is actually executing.  As such, disable this
+# optimisation.
+#
+options 	NO_ADAPTIVE_MUTEXES
+options 	NO_ADAPTIVE_RWLOCKS
+options 	NO_ADAPTIVE_SX
+
+# Xen HVM support
+options 	XENHVM
+device		xenpci