gccrs: resolve: Add ResolveExpr::funny_error

gccrs: resolve: Add ResolveExpr::funny_error

...and thread it through the constructors and the ResolveExpr::go ()
method.

This will be used for implementing the "break rust" Easter egg.

gcc/rust/ChangeLog:
	* resolve/rust-ast-resolve-expr.h,
	resolve/rust-ast-resolve-expr.cc: Add ResolveExpr::funny_error

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>