I started composing a lengthy email about why we should align 
pthread_mutex_t layout on i386 and x86_64 (because cross-process 
compatibility is of more practical importance these days than 
LinuxThreads backwards compatibility).  But then I realized that we 
don't have this choice due to the static initializers, which have __kind 
at different offsets.

The attached patch makes this more explicit in the relevant header files.

Thanks,
Florian