Update languages.yml

I'm porting to github my "auk" pre-processor language for "awk". currently, auk is in auk.googlecode.com

a ".auk" file gets converted to ".awk" after pulling out multi-line comments and add in support for structures.

when browsing, a ".auk" file, it  should be syntax highlighted as a ".awk" file

hence, i've changed languages.yml accordingly

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