also expose in-memory file method for unit testing.

SAL_UNUSED_PARAMETER (expanding to __attribute__ ((unused)) for GCC)
is used to annotate legitimately unused parameters, so that static
analysis tools can tell legitimately unused parameters from truly
unnecessary ones.  To that end, some patches for external modules
are also added, that are only applied when compiling with GCC and
add necessary __attribute__ ((unused)) in headers.

We always need to remove the index map when removing a name.

When inserting a new named range, it should overwrite any existing
name if one exists.  That was the old behavior in 3.3 prior to my
range name rework, and because of ptr_map not overwriting existing
key, that behavior had changed unintentionally.

Let's revert to the old behavior.

Especially grid lines should never be above cell borders.