honor DYNAMORIO_AUTOINJECT on linux

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on April 10, 2010 21:40:20_

with issue #85 we'll have configuration files on linux mirroring the
Windows scheme

for now we're still putting both libdrpreload.so and libdynamorio.so in
LD_PRELOAD, but we want to honor DYNAMORIO_AUTOINJECT by only putting
libdrpreload.so in LD_PRELOAD and having it load the libdynamorio.so
specified by DYNAMORIO_AUTOINJECT: allowing for more flexibility in which
DR version is used where.

to get the app name preload.c today calls DR's get_application_short_name()
which reads from /proc/self/cmdline. we'll need to either pull in all the
needed code or use another method to get the name like locating the argv
array on the stack.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=287_