Added progress indicator when generating large amounts of data.
Various fixes: Handling of sub fs, tracking of files, handling of snapshot names, vdev replace tests, import with file instead of disk-based vdev.
Fixes and enhancements in file handling.

Fixes:
 * get_rand_number: corrected call of genrand
 * make_name: make sure only characters valid in file names are returned
 * make_fs: correctly handle create option "-o property=..."
 * forget_fs: correctly escape sub fs names
 * resurrect_file: update file path correctly, if moving to new sub fs
 * get_val: correctly escape file and fs names

Enhancements:
 * new new_fifo function
 * make_file: output progress when making large files
 * print_object: use default attribute sets, if no attributes requested.
Added ashift support to "zpool add".

This adds the "-o property=value" construct to zpool add.
It also retrieves the default configured ashift value from the zpool
and uses that value if no specific ashift value has been given.
Fixed an assertion failure when looking for exported pools.
MacZFS doesn't support devids, so don't try to read these.
Changed "zpool iostat" to use the full terminal width, if needed.
Subtests numbers should start with 1.
Track success or failure of sub tests independently.
Added support for time limit for generating data.
Limit time spend on creating test files.
Added support function to simplify handling of zfs send streams.
Missing initialization of variables for separate counting of sub test failures.
Added enhanced tracing of files across snapshots and clones.
fix destroy_pool(), which was not producing a valid return code.
fixed missing local variables.
Added function for interactive inspection in a running test script.
Updated tests to utilize new tracking of files across snapshots and clones.
Updated number of tests and added an informational message while building large diskfiles.
Fixed handling of file names with "@" in the name.  Minor other fixes.
Changed interactive mode to use readline and to support custom prompt.