For each link given as http://, verify that the site is accessible over
https:// and, if so, switch to it. These domains were converted:
* llvm.org
* clang.llvm.org
* en.cppreference.com
* www.dxx-rebirth.com
* www.libsdl.org
* www.scons.org
Using precompiled headers includes vers_id.h into
similar/main/newdemo.cpp. gcc-4.9 reports a conflict between vers_id.h
`extern const char g_descent_build_datetime[21]` and newdemo.cpp macro
generated `extern const char g_descent_build_datetime[]`. The size is
only needed in the definition, so remove it from the declaration to
align with the macro-generated extern.