Improve libvroom type inference (#49)

[jimhester]

Summary

• Recognize T/F/t/f as logical values in type inference and all bool parsers
• Respect trim_ws option during type guessing (whitespace no longer stripped when trim_ws=FALSE)
• Recognize Inf/+Inf/-Inf as doubles in type inference and all float64 parsers
• Forward guess_max parameter from R to libvroom's sample_rows for type inference

Closes #49

Test Plan

• devtools::test(filter = "logical") — 14/14 pass (T/F/t/f tests unskipped)
• devtools::test(filter = "dbl") — 12/12 pass (Inf test unskipped)
• devtools::test(filter = "vroom") — 552/552 pass (guess_max and trim_ws tests unskipped)
• devtools::test() — full suite: 920 pass, 0 fail
• air format . — clean