Consider a method_decl as always being a member decl
    
    The is_member_decl() function considers that a decl is a member decl
    only if it's at class scope.
    
    In preparation for the support of incremental building of method
    decls, a method decl, even before being added to its final class, must
    always be considered as a member decl.  This allows for instance, the
    proper pretty printing of the method decl even before it's added to
    its class.
    
    This patch prepares the upcoming support of incremental building of
    method decls by making is_member_decl() work on a method_decl that
    hasn't yet been added to a class, so that is not, strictly-speaking,
    at class scope yet.
    
    	* src/abg-ir.cc (is_member_decl): Consider a method decl as always
    	being a member decl.
    	(is_member_function): Use is_member_decl.
    
    Signed-off-by: Dodji Seketeli <dodji@redhat.com>