devicemapper: split out devicemapper bindings

This is a first pass at splitting out devicemapper into separate, usable
bindings.

Signed-off-by: Vincent Batts <vbatts@redhat.com>

devicemapper/devmapper_log.go

@@ -0,0 +1,30 @@
+// +build linux
+
+package devicemapper
+
+import "C"
+
+import (
+	"strings"
+)
+
+// Due to the way cgo works this has to be in a separate file, as devmapper.go has
+// definitions in the cgo block, which is incompatible with using "//export"
+
+//export DevmapperLogCallback
+func DevmapperLogCallback(level C.int, file *C.char, line C.int, dm_errno_or_class C.int, message *C.char) {
+	msg := C.GoString(message)
+	if level < 7 {
+		if strings.Contains(msg, "busy") {
+			dmSawBusy = true
+		}
+
+		if strings.Contains(msg, "File exists") {
+			dmSawExist = true
+		}
+	}
+
+	if dmLogger != nil {
+		dmLogger.DMLog(int(level), C.GoString(file), int(line), int(dm_errno_or_class), msg)
+	}
+}