[RFC] Increase libstdc++ line length to 100(?) columns

[Jonathan Wakely <jwakely@redhat.com>]

I've touched on the subject a few times, e.g.
https://gcc.gnu.org/pipermail/gcc/2019-December/230993.html
and https://gcc.gnu.org/pipermail/gcc/2019-December/231013.html

Libstdc++ code is indented by 2 columns for the enclosing namespace,
usually another two for being in a template, and is full of __
prefixes for reserved names. On top of that, modern C++ declarations
are *noisy* (template head, requires-clause, noexcept-specifier, often
'constexpr' or 'inline' and 'explicit', and maybe some attributes.

All that gets hard to fit in 80 columns without compromising
readability with line breaks in unnatural places.

Does anybody object to raising the line length for libstdc++ code
(not the rest of GCC) to 100 columns?

Please read my replies in the thread linked above before telling me
that the code should be split up into smaller functions to avoid deep
nesting. The function I pointed to cannot easily be split up without
making the code slower to compile and potentially slower to run:
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libstdc%2B%2B-v3/include/bits/stl_algobase.h;h=a2fd306e6d0cca579b510148ba1a7089e2b2f3a2;hb=HEAD#l1499