[avr-libc-dev] Add lib per devide.

[Anatoly Sokolov]

Hello.

This patches add in the avr-libc a library per device.

I against, to build full the avr-libc library for device, this dramatically
increase compile time and the code size of avr-libc. Instead, I suggest to
build libc for architecture and add small library with device specific
functions for eeprom, wdt, boot e.t.c. modules. 

Changes in avr-libc:

1. Add libdevice subdirectory and subdirectories with device specific
libraries variants:
libdevice
eeprom libs:
|\eeprom_1d
|\eeprom_20
|\eeprom_xmega
wdt libs:
|\wdt_ver_1
|\wdt_ver_2
dummy dir:
|\none

2. Add in devtools\gen-avr-lib-tree.sh:*_DEV_INFO arrays device library name
[1] and name of subdirectory [2] with eeprom library for this device. In
addition here it is possible to customize other libraries:

AVR12_DEV_INFO="\
t90s1200:crts1200.o:libs1200[1]:${DEV_DEFS}:${CFLAGS_SPACE}:${DEV_ASFLAGS}:none[2];\
...
AVR5_DEV_INFO="\
tmega16:crtm16.o:libm16:${DEV_DEFS}:${CFLAGS_SPACE}:${DEV_ASFLAGS}:eeprom_20;\
...
tmega164p:crtm164p.o:libm164p:${DEV_DEFS}:${CFLAGS_SPACE}:${DEV_ASFLAGS}:eeprom_20;\
...
AVRXMEGA4_DEV_INFO="\
txmega64a3:crtx64a3.o:libx64a3:${DEV_DEFS}:${CFLAGS_SPACE}:${DEV_ASFLAGS}:eeprom_xmega\
e.t.c.

3. Add in  devtools\Device.am rules for building  device libraries.

Now only the "eeprom_read_byte" and "eeprom_write_byte" functions for eeprom 
library is implemented. 


The patch for GCC add the -muse-device-lib switch in GCC. 

Use the -muse-device-lib switch for automatic link the with device libraries.
For using the old avr-libc without device libraries, the -muse-device-lib
don't need. 

Anatoliy.