dmesg: implement official '-r' and colored output '-C'

Actually there is no way to have the level with the DMESG_PRETTY
-r option (raw format) is present for that in debian systems

The optional -C allow a colored output for both configs
this parameter is inspired from android logcat one.

Behavior is kept (default is raw if DMESG_PRETTY config is not set)

Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>
diff --git a/util-linux/Config.src b/util-linux/Config.src
index d2ba57c..fb62905 100644
--- a/util-linux/Config.src
+++ b/util-linux/Config.src
@@ -75,7 +75,7 @@
 	    BIOS-provided physical RAM map:
 	     BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
 
-	  Without this option you will see:
+	  Without this option (or with -r) you will see:
 	    # dmesg
 	    <5>Linux version 2.6.17.4 .....
 	    <6>BIOS-provided physical RAM map: