These are part of the Motif Developer Libraries for HP-UX 10.20 are under the
/usr/include/Motif1.2/Xm directory. The Motif Developer Libraries are
part of the 'X11MotifDevKit.MOTIF12-PRG' Motif Developers tool kit.
The Motif Development Kit is a sub-product of the 'HPUX Developers
Tool Kit', which again is part of the ANSI C bundle, and password
protected. You must have a license for the ANSI C compiler before you
can install the HPUX Developers Toolkit.
Product order information:
S800 -> B3900AA C/ANSI C Bndl
S700 -> B3393AA HP-UX Dev Tool KIt
B3898AA C/ANSI C Dev Tool Kit
It works for me (tm)