Having a static_assert on MSAN and ASAN prevents
the fuzzers from being used with different engines,
like TSAN, UBSAN, … but also with fuzzers that aren't
using MSAN/ASAN like afl for example.
* Make the Parser independent from the global C-locale
* Set a specific test locale using the environment variable FLATBUFFERS_TEST_LOCALE
* Remove redundant static qualifiers