nhc98 implementation limits

# nhc98 implementation limits Compiler limits. There are some arbitrary limits in nhc98's Prelude:
Prelude.hs | largest Eq instance for a tuple type | 15
Prelude.hs | largest Ord instance for a tuple type | 15
Runtime limits. There are various limits hard-coded into the runtime system, whose configured settings are:
node.h | max number of constructors in a data type | 512
MAX_FILE_NAME | max length of filename for profiling | 80
MAX_CDATA | max open files + ForeignObjs | 1024
HEAPSIZE | default heap (change on commandline) | 100000 words
STACKSIZE | default stack (change on commandline) | 20000 words
The latest updates to these pages are available on the WWW from `http://www.haskell.org/nhc98/` 25th September 2001 York Functional Programming Group