Example for benchmarking parsing of json files

This tries to load a file and benchmark the parsing of the file.
Note that the example is Qt5 specific, and isn't enabled by default.

Also note that it will fail if built and no input file with the right
name is present.
Provide benchmark code string to double conversion

This example file benchmarks QLocale's string to double conversion
over the native linux locale strtod_l function for string to double
conversion.

This benchmark is not built or run by default of testing because it
isn't that useful as a general thing, but can serve for inspiration for
later.
Merge pull request #43 from svuorela/benchmarks

Benchmarks