* lisp/progmodes/xref.el (xref--insert-xrefs): Cut up the current
line into pieces here for multiple matches's summaries, so that
xref--insert-xrefs can do less work (bug#46859).
(xref--insert-xrefs): Do less work.
(xref--outdated-p):
Update accordingly to how the summary creation logic changed.
(xref--buf-pairs-iterator): Update to the new calling convention.
(xref-location-column): Effectively rename back to
xref-file-location-column since the generic version is now unused.

* test/lisp/progmodes/xref-tests.el
(xref-matches-in-directory-finds-two-matches-on-the-same-line)
(xref-matches-in-directory-finds-an-empty-line-regexp-match):
Adjust to the xref-location-column change.
(xref-matches-in-files-trims-summary-for-matches-on-same-line):
New test.

* test/lisp/progmodes/xref-resources/file1.txt:
Change contents slightly to test the new xref--outdated-p code.

* test/data/emacs-module/mod-test.c: Move from here...
* test/src/emacs-module-resources/mod-test.c: ...to here.
* test/src/emacs-module-tests.el (ert-x): Require.
(mod-test-file, module/describe-function-1):
* test/Makefile.in (test_module_dir): Adjust for move.

* test/data/files-bug18141.el.gz: Move from here...
* test/lisp/files-resources/files-bug18141.el.gz: ... to here.
* test/lisp/files-tests.el (ert-x): Require.
(files-test-bug-18141-file): Use ert-resource-file.

* test/data/mailcap/mime.types: Move from here...
* test/lisp/net/mailcap-resources/mime.types: ...to here.
* test/lisp/net/mailcap-tests.el (ert-x): Require.
(mailcap-tests-path): Use ert-resource-file.

* test/data/somelib.el:
* test/data/somelib2.el: Move from here...
* test/src/lread-resources/somelib.el:
* test/src/lread-resources/somelib2.el: ...to here.
* test/src/lread-tests.el (ert, ert-x): Require.
(lread-test-bug26837): Use ert-resource-directory.

* test/data/syntax-comments.txt: Move from here....
* test/src/syntax-resources/syntax-comments.txt: ...to here.
* test/src/syntax-tests.el (ert-x): Require.
(syntax-comments, syntax-br-comments, syntax-pps-comments):
Use ert-resource-file.

* test/data/xref/file1.txt:
* test/data/xref/file2.txt: Move from here...
* test/lisp/progmodes/xref-resources/file1.txt:
* test/lisp/progmodes/xref-resources/file2.txt: ...to here.
* test/lisp/progmodes/xref-tests.el (ert, ert-x): Require.
(xref-tests-data-dir): Use ert-resource-directory.