Changes in revision 106420 reverted

[Eli Zaretskii]

Sorry about that.

I reverted these because the functions I made external are explicitly
intended to be that.  I don't want to need to convert them back from
static when they are called from outside the module that defines them.
Hash codes of glyph rows are manipulated both in xdisp.c and in
dispnew.c, so the natural thing for these functions is to be external,
not static.

Besides, code like this:

 #if !XASSERTS
 static
 #endif
 unsigned
 row_hash (struct glyph_row *row)
 {

is butt-ugly, IMNSHO.  There's a limit to which we should go to pacify
overly-pedantic compiler switches, and this is way out.