checkpackagelib/lib_config.py: check packages alphabetical order in {Config.in, Confi...

checkpackagelib/lib_config.py: check packages alphabetical order in {Config.in, Config.in.host}

Signed-off-by: Jerzy Grzegorek <jerzy.m.grzegorek@gmail.com>
[Arnout:
 - calculate level by counting - instead of with a static array;
 - new_package is only used locally, so don't make it a class member;
 - do indentation according to length of prefix;
 - don't split string in the middle of a line;
 - report first wrong package per menu;
 - do replace() only once;
 - add comment why we do replace().
]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>