Simplify build system architecture optimization

This change to the build system rips out any usage of PROC along with
architecture-specific optimizations in favor of using -march=native where it is
supported.  This fixes broken builds on 64bit Intel systems and results in
better optimized code on systems running GCC 4.2+.

Review: https://reviewboard.asterisk.org/r/1852/
(closes issue ASTERISK-19462)
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Merged revisions 361955 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 361956 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@361968 65c4cc65-6c06-0410-ace0-fbb531ad65f3