FIX: ASSERT_DEATH() segfaults for no obvious reason under SLC6
Merge pull request #179 from reneme/fix_slc6_unittest

FIX: ASSERT_DEATH() segfaults for no obvious reason under SLC6

googletest uses clone() to spawn a new process when using ASSERT_DEATH(). For no obvious reason this segfaults and interrupts the test run on SLC6 x64. Fortunately one can configure googletest to use fork()/_exit() instead, which works fine.