dtc: Improve -Odts output

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> This patch makes improvements to the way properties are printed when
> in dtc is producing dts output.  
> 	- Characters which need escaping are now properly handled when
> printing properties as strings
> 	- The heuristics for what format to use for a property are
> improved so that 'compatible' properties will be displayed as
> expected.
> 	- escapes.dts is altered to better demonstrate the changes,
> and the string_escapes testcase is adjusted accordingly.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl