Fix the fact that previously strtof/d/ld would only accept a NaN as
having parentheses if the thing in the parentheses was a valid number,
now it will accept any combination of letters and numbers, but will only
put valid numbers in the mantissa.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D113790

Update binaryExpTofloat so that it will round correctly for long inputs when converting hexadecimal strings to floating points.

Differential Revision: https://reviews.llvm.org/D113815

When strtof/d/ld return a subnormal number they may set errno to
ERANGE. This change makes this behavior more consistent by making any
decimal number converting to a subnormal set errno to ERANGE. This
brings it in line with hexadecimals, which currently only set errno to
ERANGE if the number is truncated when converting to a subnormal.

Reviewed By: sivachandra, lntue

Differential Revision: https://reviews.llvm.org/D113626

Split the code for parsing hexadecimal floating point numbers from the
code for parsing the decimal floating point numbers so that the parsing
can be faster for both of them.

This decreases the time for the benchmark in release mode by about 15%,
which noticeably beats GLibc.

Old version: 2.299s
New version: 1.893s
GLibc: 2.133s

Tests run by running the following command 10 times for each version:
time ~/llvm-project/build/bin/libc_str_to_float_comparison_test ~/parse-number-fxx-test-data/data/*

the parse-number-fxx-test-data-repository is here:
https://github.com/nigeltao/parse-number-fxx-test-data/tree/fe94de252c691900982050c8e7c503d1efd1299a

It's important to build llvm-libc in Release mode for accurate
performance comparisons against glibc (set -DCMAKE_BUILD_TYPE=Release in
your cmake).
You also have to build the libc_str_to_float_comparison_test target.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D113036

Previously, strtol/ll/ul/ull would return a pointer to the end of its
parsing, regardless of if it detected a number. Now it will return a
length of 0 when it doesn't find a number.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D112176

Add the string to floating point conversion functions.
Long doubles aren't supported yet, but floats and doubles are. The
primary algorithm used is the Eisel-Lemire ParseNumberF64 algorithm,
with the Simple Decimal Conversion algorithm as backup.

Links for more information on the algorithms:

Number Parsing at a Gigabyte per Second, Software: Practice and
Experience 51 (8), 2021 (https://arxiv.org/abs/2101.11408)
https://nigeltao.github.io/blog/2020/eisel-lemire.html
https://nigeltao.github.io/blog/2020/parse-number-f64-simple.html

Differential Revision: https://reviews.llvm.org/D109261

A fuzzer for qsort has also been added.

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D110382

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D110222

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D109952

Fix edge case where "0x" would be considered a complete hexadecimal
number for purposes of str_end. Now the hexadecimal prefix needs a valid
digit after it, else just the 0 will be counted as the number.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D109084