Recent testing has uncovered some hard-to-find bugs in printf's long
double support. This patch adds an extra long double path to the fuzzer
with minimal extra effort. While a more thorough long double fuzzer
would be useful, it would need to handle the non-standard cases of 80
bit long doubles such as unnormal and pseudo-denormal numbers. For that
reason, a standalone long double fuzzer is left for future development.
To guarantee accuracy for all potential float values, this patch adds a
fuzzer to compare the results for float conversions from our printf
against MPFR's.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D156495
