hdf5_msb

[svn-r26081] Moved the check for pthread_attr_setscope() into the thread-safe checks
section. Documented its necessity and added a cross-compiling option
and helpful comment.

Also removed a check for BSDgettimeofday from configure.ac, which
was for Irix 5.3 support.

Part of HDFFV-9087

Tested on: jam with threadsafe