r10-11132 uses C++11 default member initializers, which breaks bootstrapping
with a C++98 compiler.
gcc/ChangeLog:
* doc/install.texi: 10.5 won't bootstrap with C++98.
for used C++14 features.
Versions of GCC prior to 15 allow bootstrapping with an ISO C++11
-compiler, versions prior to 11 allow bootstrapping with an ISO C++98
+compiler, versions prior to 10.5 allow bootstrapping with an ISO C++98
compiler, and versions prior to 4.8 allow bootstrapping with an ISO
C89 compiler.