.functions: Add `calc`
.bash_profile: Move the `LANG` & `LC_ALL` exports into `.exports`
.osx: Remove the iTunes Ping settings

Apple officially closed the iTunes Ping service on September 30th, 2012 (http://i.imgur.com/U7bHo.jpg).
.osx: Document the various values for Hot Corners settings
.osx: Clarify that the iTunes settings are for pre-iTunes 11 only
Improve `httpcompression`

- correctly detect `SDCH` compression, see:
  http://www.blogs.zeenor.com/wp-content/uploads/2011/01/Shared_Dictionary_Compression_over_HTTP.pdf
- correctly overwrite the user agent (use the -A, not the -H option)
- limit the connection and operation time (useful for preventing curl
  from hanging for hours due to slow networks or links going down)
- show errors
- show redirects