Projects that link simdjson from MSVC with exceptions off will
include simdjson headers which transitively include STL headers.
The MSVC STL stipulates that _HAS_EXCEPTIONS=0 be defined or code
requiring exceptions will be enabled. This change adds a new job
to the appveyor build matrix to verify the build and tests with
exceptions disabled, and disables exceptions at the compiler level
when SIMDJSON_EXCEPTIONS is specified to OFF.
* add definitions for is_number and tie (by lemire)
* add fuzzer for element
* update fuzz documentation
* fix UB in creating an empty padded string
* don't bother null terminating padded_string, it is done by the std::memset already
* refactor fuzz data splitting into a separate class