This adds --empty=create and --size= for creating loopback files from
scratch of a specified size, or growing loopback files to the specified
size when they already exist.
This is useful when operating on disk image files, as a manual
invocation of fallocate(1) becomes unnecessary.
The enum used for column names is integer type while table_set_display() is parsing
arguments on size_t alignment which may result in assert in table_set_display() if
the size between types missmatch. This patch cast the enums to size_t.
It also fixes all other occurences for table_set_display() and
table_set_sort().