HAL RTC parameters fix

[Nick Garnett <nickg at ecoscentric dot com>]

The attached patch converts all the HALs to define the RTC constants
with "default_value" rather than "calculated". This makes it easier to
redfine the clock rate. The old mechanism of using the
CYGPKG_KERNEL_COUNTERS_CLOCK_OVERRIDE component did not work very
well, since many HALs reference CYGNUM_HAL_RTC_PERIOD directly. As
they must to avoid introducing unnecessary dependencies on the kernel.

The patch consequently eliminates the
CYGPKG_KERNEL_COUNTERS_CLOCK_OVERRIDE component. The only real worry
is that a little useful documentation has been lost -- I'm looking at
adding something to the HAL documentation to compensate.

While this is a simple change, it does touch a lot of files. Hence it
is being posted here for comments before being applied.

Attachment: rtc.override.gz
Description: RTC parameter patch

-- 
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com      The eCos and RedBoot experts