ld: improve linker script section

ld: improve linker script section

The example version script in the manual currently suggests:
	extern "C++" { "int f(int, double)"; }

But a C++ function like that doesn't encode the return type into the
mangled  name, so when the linker demangles things, it ends up with
"f(int, double)"  and so it never matches.

The example also lacks a trailing semicolon after the brace, so the
linker always complains about a syntax error in the file.

While the language section documents the possibilities, it isn't clear
as to which is the default language.  So explicitly state that the C
language is the default.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>