Let's rename the printing functions so their names look more like
the standard ones.

1. putc/puts with a file descriptor.

__std_putc -> std_dputc
__std_puts -> std_dputs

There are no standard putc/puts that accept fd as an argument,
but the libc convention is to use d prefix for such. Therefore:

NOTE we keep the order of the arguments intact, to be in line
with the rest of the functions.

2. *printf

__std_printk -> std_vdprintf
__std_printf -> std_dprintf

The reason is, these are the names of libc functions with similar
functionality/arguments.

Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>