Eliminates lots of overhead.

The _GLIBCXX_USE_C99_MATH macro is defined in glibcxx by c++config.h, which
gets included by every header. Which means a header needs to be present.

_exit and std::_Exit are identical, expect the latter is standard C++.

Added several functions to the std namespace as a result of headers.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with readability-uppercase-literal-suffix
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is the case with uClibc-ng currently.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry picked from commit 769cd0ee9f0cf8ceb026aa751b5d4a390bb5dbdc)
(changed define to match master)

This has nothing to do with uClibc. It has everything to do with gcc's
libstdc++.

C99 math can be compile time disabled for it. Check for that and use boost
lround when std is not available.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

lrint is a configurable version of lround that behaves either as round,
floor, ceil, or trunc based on setting the proper FE_ macro using
fset/getround. Given that it's not set at all and that it defaults to
round behavior, simply replace with round.

Also removed the util/Math defines.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

It's available there.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

[[maybe_unused]] (introduced in C++17) is standard C++.

https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
says that this is equivalent to the GNU unused attribute.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

[[nodiscard] (introduced in C++17) can be used instead.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

[[deprecated]] (introduced in C++14) may be used instead.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Boost does not seem to offer an overload for lrint.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is the case with uClibc-ng currently.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Fixes Windows build failure.

The former is deprecated by C++14. The standard says they are the same:

The header defines all types and macros the same as the C standard library
header<stdint.h>.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former is deprecated with C++14. The standard says both are the same:

The contents and meaning of the header<cstddef>are the same as the C
standard library header<stddef.h>,except that it does not declare the type
wchar_t, that it also declares the type byte and its associated
operations (21.2.5), and as noted in 21.2.3 and 21.2.4.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated in C++14. The Standard says they are the same:

The contents of the header<cstdarg>are the same as the C standard library
header<stdarg.h>, with the following changes: The restrictions that ISO C
places on the second parameter to the va_start macro in header<stdarg.h>
are different in this International Standard. The parameter parmN is the
rightmost parameter in the variable parameter list of the function
definition (the one just before the...).219If the parameter parmN is a
pack expansion (17.5.3) or an entity resulting from a lambda capture
(8.1.5), the program is ill-formed, no diagnostic required. If the
parameter parmN is of a reference type, or of a type that is not
compatible with the type that results when passing an argument for which
there is no parameter, the behavior is undefined.

Also changed va_list to the std:: namespace version, which is the same.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Get rid of the macro hell.