Windows: product names, the editors, WSL; the Linux page's image step

Assembled from development commit c3c40f6c8fca. Since 830b193: on Windows the
products carry Windows names (ktext.exe, klammertext.dll, document.dll,
reflect.dll) and the console's output code page is UTF-8 for a run; the
editor tooling works on Windows (VS Code, Sublime Text, Vim, with the
interpreter's name chosen by platform) and Notepad++ joins it
(doc/edit/notepadpp: a User Defined Language and two Run-menu commands);
a sixth install page, doc/install/windows_wsl_install.md, for Linux
inside WSL; the Windows page opens with the three routes and gains its
editor section, the PowerShell quoting and Path notes; the Linux page
installs OpenImageIO from the python3-openimageio package and verifies
with kdiag --machine; the README lists all six install pages. Linux and
macOS behaviour is unchanged.

tst/klammerset_test.sh

@@ -86,7 +86,10 @@ check_contains() {
         FAIL=$((FAIL + 1))
         return
     fi
-    if printf '%s' "$output" | grep -qF "$needle"; then
+    # Wrap-insensitive: error text is justified to 80 columns, and where the
+    # needle breaks across a line depends on the installation's path length
+    # (found in Windows Sandbox, whose user name is long: "was not \nfound").
+    if printf '%s' "$output" | tr '\n' ' ' | tr -s ' ' | grep -qF "$needle"; then
         echo "${green}PASS${reset} $test_name"
         PASS=$((PASS + 1))
     else
@@ -114,7 +117,8 @@ check_fails() {
         FAIL=$((FAIL + 1))
         return
     fi
-    if printf '%s' "$output" | grep -qF "$needle"; then
+    # Wrap-insensitive, like the other helper above.
+    if printf '%s' "$output" | tr '\n' ' ' | tr -s ' ' | grep -qF "$needle"; then
         echo "${green}PASS${reset} $test_name"
         PASS=$((PASS + 1))
     else