include sys/param.h in getcwd.c

[Roland McGrath]

> I came across this 2006 patch 
> <http://sourceware.org/ml/libc-alpha/2006-06/msg00068.html> in the course 
> of reviewing bugs.  I think it should go in as an obvious fix - source 
> files should use well-defined APIs of the headers they include rather than 
> relying on long indirect include paths for internal headers.  Comments?

Yes, including directly what you actually use is just common sense.