Use safe getenv for setting up backtrace capturing method
Use safe getenv for setting up backtrace capturing method

This code runs very early, so using special "early" version of getenv
is reasonable. It should fix issue #912.

acmorrow/gperftools,acmorrow/gperftools,alk/gperftools,romange/gperftools,gperftools/gperftools,alk/gperftools,romange/gperftools,alk/gperftools,acmorrow/gperftools,acmorrow/gperftools,gperftools/gperftools,alk/gperftools,romange/gperftools,gperftools/gperftools,gperftools/gperftools,romange/gperftools