strtoll, strtoull

[Charles Wilson]

Recently, patches were accepted to implement long long and unsigned long 
long functionality for the scanf family of functions.  This was done 
using new private functions __strtoull_r and __strtoll_r.  However, this 
functionality was not exported.

So, I've renamed __strtoull_r and __strtoll_r to _strtoull_r and 
_strtoll_r (following the pattern of _strtod_r), as well as implemented 
new functions strtoull and strtoll.  This involves the attached patch as 
well as two new files: newlib/libc/stdlib/strtoull.c and 
newlib/libc/stdlib/strtoll.c.  All four functions are now declared in 
stdlib.h.

--Chuck