kernel: let banner output by normal channel

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
kdb:  select DEBUG when using kdb

Developer requires debug I/O channel to communicate with KDB

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
kernel: resolve compile time warning

kernel/softirq.c:27:14: error: 'softirq_names' defined but not used

Reserve softirq_names for future use

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
lib: resolve conflict type definition

Resolve the following error,
  In file included from arm-2013.05/bin/../lib/gcc/arm-none-eabi/4.7.3/
                      ../../../../arm-none-eabi/include/stdio.h:34:0,
                 from kernel/start.c:26:
                      arm-2013.05/bin/../lib/gcc/arm-none-eabi/4.7.3/
                      include/stddef.h:213:23: error: conflicting types for 'size_t'
  In file included from include/platform/debug_uart.h:9:0,
                 from kernel/start.c:13:
    include/types.h:17:18: note: previous declaration of 'size_t' was here

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
lib: make debug macro more solid when CONFIG_DEBUG is not defined

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
kernel: wrapper implicit kdb-related code by CONFIG_KDB

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
lib: divide stdio port from debug port

The choice of CONFIG_STDIO_xxxx is used to select STDIO port.
There are 2 choices now,
 1. CONFIG_STDIO_USE_DBGPPORT: use debug uart as stdio device
 2. CONFIG_STDIO_NODEV: null stdio device.

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
debug: make debug port selectable

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
debug: clean up sources

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
lib: tweak stdio functions

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
debug: move device function declaration to debug_device.h

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
lib: tweak return value of getchar

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
debug: exclude KDB and non-uart stdio port

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
Merge pull request #49 from vh21/tweak-dbg

Refine debug I/O facilities
Kconfig: tweak debug options