Fix benchmarks on Windows and add trimmed variants

[andreivasiliu]

Mostly so I can test #208 easily. I tested it on both Windows and Linux.

running 10 tests
test bench_quick_xml_escaped                   ... bench:     287,112 ns/iter (+/- 39,689)
test bench_quick_xml_escaped_trimmed           ... bench:     261,086 ns/iter (+/- 4,760)
test bench_quick_xml_namespaced                ... bench:     369,875 ns/iter (+/- 8,434)
test bench_quick_xml_namespaced_trimmed        ... bench:     382,590 ns/iter (+/- 8,347)
test bench_quick_xml_normal                    ... bench:     232,672 ns/iter (+/- 2,766)
test bench_quick_xml_normal_trimmed            ... bench:     247,441 ns/iter (+/- 3,108)
test bench_quick_xml_one_cdata_event_trimmed   ... bench:          86 ns/iter (+/- 0)
test bench_quick_xml_one_comment_event_trimmed ... bench:          84 ns/iter (+/- 0)
test bench_quick_xml_one_start_event_trimmed   ... bench:         112 ns/iter (+/- 1)
test bench_quick_xml_one_text_event            ... bench:          61 ns/iter (+/- 2)

test result: ok. 0 passed; 0 failed; 0 ignored; 10 measured; 0 filtered out

[tafia]

Thanks!