virt: check for /sys/hypervisor/type for detecting xen PV

https://bugs.freedesktop.org/show_bug.cgi?id=61491
man: Fix id attributes
man: Unify title for configuration files
util: Fix grammar in comment
bootchart: add parameter "-C" to expand process names to the full cmdline
bootchart: rename global len to samples_len
bootchart: use _cleanup_fclose_