Hi,

This is what i came up with in response to the presence of a number of 
macros to access ptid members and to do ptid-related checks.

I've dropped all the macros and used the underlying implementation where 
suitable. New functions were created (ptid_is_lwp, ptid_is_tid) to do 
additional checks without the need of macros.

I've grouped the null_ptid and minus_one_ptid checks inside 
ptid_is_invalid to reuse existing code.

A run from the testsuite tells me there are no regressions.

I've been extra careful to convert from the ptid-building macros to the 
ptid_build function since sol-thread.c and aix-thread.c had some 
variations regarding the position of TID/LWP inside the ptid. Please 
double check.

Luis