I have written a replacement command for the C Library Bundle and placed in the C Bundle. Type at least the first letter in the function you want to autocomplete and hit ctrl-M, this will bring up a menu where you can choose which function you want to complete. The completions are stored in the file CLib.txt.gz, add that file to the Support folder in the C Bundle in. The completions where taken from the (now removed) C Library Bundle running the following command in the Snippet folder.
ruby -e "Dir["*"].each do |name| puts open(name).read.match(/content</key>\n\s*<string>(.*)/)[1] end"
if for some reason CLib.txt.gz is to large for the list use that to generate CLib.txt and gzip it.