Fix/remove duplicate console message

[lrascao]

No description provided.

[ghost]

Can you please make the following minor changes?

1. rebase cleanly against master (maybe git reset --hard origin/master && git cherry-pick 6bba389 followed by git commit --amend for the commit message fix)
2. fix the commit message to properly follow CONTRIBUTING

before

remove duplicate compiling message

unnecessary since base compiler already prints a message to the effect

after

gpb_compiler: remove duplicate compiling message

It's unnecessary to print "Compiling..." since base_compiler already prints a
message to the effect.

[lrascao]

@Tuncer, done

[ghost]

ping @ferd @tsloughter?