arrow

ARROW-621: [C++] Start IPC benchmark suite for record batches, implement "inline" visitor. Code reorg

From the benchmarks, the difference between virtual functions and an "inline" switch statement is very small, but it serves to reduce some boilerplate when many of the visit functions are the same

Author: Wes McKinney <wes.mckinney@twosigma.com>

Closes #427 from wesm/ARROW-621 and squashes the following commits:

b975053 [Wes McKinney] cpplint
782636a [Wes McKinney] Mark template inline
3ae494e [Wes McKinney] Inline visitor, remove code duplication in loader.cc in favor of templates / std::enable_if
1b2d253 [Wes McKinney] Tweak benchmark params
b126ca8 [Wes McKinney] Draft IPC roundtrip benchmark for wide record batches. Some test code refactoring