os test: do not use symlink > 255 bytes.
os test: do not use symlink > 255 bytes.

Fixes issue 62.

R=r
http://codereview.appspot.com/152080

pombredanne/go-deleteme,dsriram/golang,gnanderson/go,tianon/debian-golang,ssrl/go,tv42/old-go,nightlyone/golang,nightlyone/golang,apparentlymart/golang,ssrl/go,gnanderson/go,nightlyone/golang,h8liu/golang,tianon/debian-golang,tianon/debian-golang,apparentlymart/golang,tv42/old-go,apparentlymart/golang,bdwalton/debian-golang,tv42/old-go,tianon/debian-golang,ssrl/go,dsriram/golang,pombredanne/go-deleteme,dsriram/golang,pombredanne/go-deleteme,dsriram/golang,h8liu/golang,ssrl/go,ssrl/go,bdwalton/debian-golang,gnanderson/go,h8liu/golang,pombredanne/go-deleteme,bdwalton/debian-golang,h8liu/golang,ssrl/go,nightlyone/golang,tv42/old-go,h8liu/golang,tianon/debian-golang,pombredanne/go-deleteme,apparentlymart/golang,tianon/debian-golang,tv42/old-go,bdwalton/debian-golang,nightlyone/golang,pombredanne/go-deleteme,tianon/debian-golang,gnanderson/go,tv42/old-go,dsriram/golang,pombredanne/go-deleteme,h8liu/golang,gnanderson/go,nightlyone/golang,dsriram/golang,gnanderson/go,tianon/debian-golang,apparentlymart/golang,h8liu/golang,apparentlymart/golang,gnanderson/go,apparentlymart/golang,bdwalton/debian-golang,tv42/old-go,dsriram/golang,ssrl/go,bdwalton/debian-golang,nightlyone/golang,bdwalton/debian-golang,bdwalton/debian-golang