std_limits.h os_defines.h

[David Edelsohn]

>>>>> Benjamin Kosnik writes:

Ben> Please make sure that what every you come up with allows 
Ben> newlib-based cross compilers to work (ie, test on x86-linux cross 
Ben> powerpc-eabism)

	May I point out that limits_generic.h has incorrect information
for powerpc-eabism?  PowerPC defaults to unsigned char, but
limits_generic.h always reports signed char.  There are lots of corner
cases like this where limits_generic.h appears to work, but really reports
incorrect information.

David