PR18417: Increase -ftemplate-depth to the value 1024 recommended by the C++

standard's Annex B. We now attempt to increase the process's stack rlimit to
8MiB on startup, which appears to be enough to allow this to work reliably.
(And if it turns out not to be, we can investigate increasing it further.)


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@278983 91177308-0d34-0410-b5e6-96231b3b80d8