The call to abi::__cxa_demangle() with too small of a char[] can cause
segfaults or hangs.   This change increases the array from 256 to 4096.

Bug: angleproject:3553
Test: Verify validation layers don't segfault/hang
Change-Id: I6704ff00bfab62c99eb288f803ccda35a037dd9d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1670580Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Tim Van Patten <timvp@google.com>