Prepare OTP files for Unicode as default encoding
eunit: Eliminate use of the package syntax
Implement ./otp_build configure --enable-silent-rules

With silent rules, the output of make is less verbose and compilation
warnings are easier to spot. Silent rules are disabled by default and
can be disabled or enabled at will by make V=0 and make V=1.
Merge branch 'nox/enable-silent-rules/OTP-10726'

* nox/enable-silent-rules/OTP-10726:
  Implement ./otp_build configure --enable-silent-rules
Prepare release