Add option for architecture in Makefile

In this merge request:

• Add an option to add gcc architecture option in main Makefile (-m32, -m64, etc.)
• Use a more idiomatic way to call sub Makefiles

added 1 commit

• f6ecb635 - Replace -m64 by -m32

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added 3 commits

• 603067f9 - 1 commit from branch brateau2015:master
• d448bc97 - Add option for architecture in Makefiles
• a99e9e12 - Replace -m64 by -m32

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merged