Hi,

The attached patch adds logging support for sid components in 3 stages:

1) Add a new level to the sid component heirarchy

    o fixed_attribute_map_with_logging_component inherits 
fixed_attribute_map_component and provides the logging capability
    o An output pin, ulog_out_pin, is defined here through which the log 
data is output.
    o printf-like logging (my immediate need) is provided via the 'void 
log (level, const char *fmt, ...)' method
    o Attributes record the logging settings (see options below)
    o A nice future addition would be a 'log (level)' method which would 
return some kind of stream object.

2) Add capability to sid-io-stdio (sid/consoles/stdio.cxx) for writing 
output to a file.

    o This provides logging to stdout or to a via via the component's 
ulog_out_pin

3) Expand the command line interface for sid

    o 3 new options control logging behavior
        --ulog-level=INTEGER
        --ulog-mode={less|match|equal}
        --ulog-file=FILENAME
    o As with many options, these relate to the previous --board 
specified or provide settings for all boards if specified before the 
first --board option.
    o The board level settings are kept in BoardCfg 
(sid/main/dynamic/commonCfg.h) by inhereting a new UlogCfg
    o The global level settings are kept in SessionCfg also by inherting 
from UlogCfg
    o Configuration may then use this info to set attributes and connect 
pins in the desired components to activate the logging feature.

NOTES:
o I needed to use vsnprintf or vasprintf if available and so I added 
checks for them in sid/component/configure.in
o I needed to define _ISOC99_SOURCE for vsnprintf or _GNU_SOURCE for 
vasprintf and so we now also have to define _BSD_SOURCE and _SVID_SOURCE 
which are normally defined by default if no _XXXXX_SOURCE is defined.
o I included the regenerated sid/component/config.h in the patch so you 
can see the new macros.

I'm requesting review of this patch, especially the placement of the new 
functionality in the component heirarchy and the configury changes to 
sid/component.

Thanks,
Dave