The above method definitely works. Tested in:
MacBook Air
Os X Mavericks 10.9.4
JRE 7u61 & 8u11
However, it should be faster to do:
Open Finder
Press Shift+Command+G
Type in "~/Library/Application Support/technic/modpacks/tekkit/bin/natives"
Rename libjwjgl.jnilib to libjwjgl64.dylib
--OR--
Open terminal, and enter the command:
cd ~
mv "Library/Application Support/technic/modpacks/tekkit/bin/natives/liblwjgl.jnilib" "liblwjgl64.dylib"
You might have to tweak the paths... I'm not too good with *nix bash commands
