Changes to Libfiber between r1 and r2

'''Simple Fiber Library'''

http://evanjones.ca/software/threading.html [http://www.rkeene.org/projects/info/resources/threads/libfiber/threading.html]
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Implementation of [fibers] (for [cooperative threading]) --> Implementation of [fibers] (for [cooperative threading]) using 3 different techniques:
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http://evanjones.ca/software/threading.html [http://www.rkeene.org/projects/info/resources/threads/libfiber/threading.html]
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   * setjmp()/longjmp()
   * ucontext()
   * Linux's clone()
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Each implementation provides the same API, so they can be used interchangeably.
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Mirror of source: http://www.rkeene.org/projects/info/resources/threads/libfiber/libfiber.tar.gz
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Sample application using Libfiber: http://www.rkeene.org/projects/info/resources/threads/test1-lf.c

Compile:
   * $ cc -o test1-lf test1-lf.c libfiber-sjlj.c''; or''
   * $ cc -o test1-lf test1-lf.c libfiber-uc.c''; or''
   * $ cc -o test1-lf test1-lf.c libfiber-clone.c

Legend

     Only in r1
     Only in r2
     -->      Modified slightly between r1 and r2