style: [patch 1/22] use /r/3648/ to reorganize includes

style: fix missing spaces in control statements

Result of running 'hg m5style --skip-all --fix-control -a'.

sim: Add support for generating back traces on errors

Add functionality to generate a back trace if gem5 crashes (SIGABRT or
SIGSEGV). The current implementation uses glibc's stack traversal
support if available and stubs out the call to print_backtrace()
otherwise.