... whenever they really describe the size of a buffer that fits in memory, or
of a block file (which is never now more than a megabyte and so could be fit in
memory all at once), or a part thereof.
... A non-narrowing conversion out to long long is a necessity, but the
conversions to float and double are simply conveniences.
Conversion from floating is explicit, to avoid unintended consequences with
arithmetic operators, when later sampleCount ceases to be an alias for an
integral type.
Some conversions are not made explicit, where I expect to change the type of
the variable later to have mere size_t width.
...They may never have been large enough to matter, but some seek offsets into
files were written as 64 bits but read back as only 32. It ought to be
consistent.
better handling of error conditions in all BuildFromXML methods, per comment:
// BuildFromXML methods should always return a BlockFile, not NULL,
// even if the result is flawed (e.g., refers to nonexistent file),
// as testing will be done in DirManager::ProjectFSCK().
