EPS import: a PostScript error shows what its name means in the interface language

An EPS or PostScript file that stops on a PostScript error named the
error, such as typecheck or rangecheck, with the operator and the
procedure, but did not say what the name means in any language.

The warning or error now gives the name as PostScript spells it,
followed by VectorCraft's own wording of what it means in the reader:
"a PostScript error (typecheck in `add`; a value has the wrong type for
the operator)". vectorcraft_eps::POSTSCRIPT_ERRORS lists the 14 names
the reader raises other than undefined, with their meanings, and a
test checks that each of those names has one. Each meaning and the
new message shapes have a row in every catalog. i18n::message now
translates placeholder values five levels deep instead of three, which
the status bar's line for an EPS file that can't be opened needs.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -3519,7 +3519,9 @@ point type in the font the file names (embedded font programs are skipped). In a
 (else `%%BoundingBox`; a letter page without one). A program the interpreter can't run (an operator it doesn't know,
 an error, a runaway loop) or that draws nothing comes in as its TIFF preview (palette previews with an alpha channel
 too) with a warning; without a preview, the art drawn up to the error is kept with a warning, and a file with none is
-refused with a message saying why.
+refused with a message saying why. A PostScript error is named as PostScript spells it, followed by what it means:
+``a PostScript error (typecheck in `add`; a value has the wrong type for the operator)``. The status bar shows
+the meaning in the interface language, and the name stays as it is.
 
 ```json
 {"name":"run_command","arguments":{"command":"document.open","params":{"path":"/tmp/logo.eps"}}}