Add descriptions and homepages to gcc related packages

Add ffmpeg package

Strip some common packages

Refactor dependency expansion

Change crew to hide `buildessential` from dependencies list since it is a fake package.
Change crew to not check :build dependencies if a target is already installed.
Chagen crew to remove unnecessary push_dependency call.
Change package.rb to update comments

Also add check method.

Adding cmatrix package

Add readline dependency to R

DEBUG_SYMBOLS modification

Update openssl to 1.0.2l and distribute with pre-built arm binaries

Update mlocate homepage url

Change openssl.rb to strip binary and libraries and prepare to install man correctly.
Also add check method to check the correctness.

  - Remove libvpx package

  - Add libfontconfig configure option
  - Remove target configure option from libvpx

Correct scrollz

Update mandb to 2.7.6.1 and strip binary and libraries.

Change python27.rb to add check method and optimize for size

Modify dependencies in several packages.

Change to use tar for the performance