Add aaaaaa_*.xml with unreasonably large tokens

Some of these currently take a very long time to parse. I set those to
only run one loop in the run-benchmark make target.

4096 may be a fairly small buffer, and definitely make the problem worse
than it otherwise would've been, but similar sizes exist in real code:

 * 2048 bytes in cpython Modules/pyexpat.c
 * 4096 bytes in skia SkXMLParser.cpp
 * BUFSIZ bytes (8192 on my machine) in expat/examples

The files, too, are inspired by real-life examples: Android stores
depth and gain maps as base64-encoded JPEGs inside the XMP data of
other JPEGs. Sometimes as a text element, sometimes as an attribute
value. I've seen attribute values slightly over 5 MiB in size.

expat/Makefile.am

@@ -131,6 +131,11 @@ buildlib:
 run-benchmark:
 	$(MAKE) -C tests/benchmark
 	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/recset.xml 65535 3
+	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/aaaaaa_attr.xml 4096 3
+	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/aaaaaa_cdata.xml 4096 3
+	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/aaaaaa_comment.xml 4096 3
+	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/aaaaaa_tag.xml 4096 3
+	./run.sh tests/benchmark/benchmark@EXEEXT@ -n $(top_srcdir)/../testdata/largefiles/aaaaaa_text.xml 4096 3
 
 .PHONY: download-xmlts-zip
 download-xmlts-zip:

testdata/largefiles/README.txt

@@ -31,4 +31,27 @@ resulting measurements tell us.)
     utility, specifically for testing the duplicate attribute check in
     storeAttributes()
 
+* aaaaaa_attr.xml (~10 MB):
+  - properties: trivial file with a huge attribute value
+  - source: generated by a simple shell script
+  - purpose: performance/regression test
 
+* aaaaaa_cdata.xml (~10 MB):
+  - properties: trivial file with huge cdata content
+  - source: generated by a simple shell script
+  - purpose: performance/regression test
+
+* aaaaaa_comment.xml (~10 MB):
+  - properties: trivial file with a huge comment
+  - source: generated by a simple shell script
+  - purpose: performance/regression test
+
+* aaaaaa_tag.xml (~10 MB):
+  - properties: trivial file with a huge tag name
+  - source: generated by a simple shell script
+  - purpose: performance/regression test
+
+* aaaaaa_text.xml (~10 MB):
+  - properties: trivial file with a huge text segment (no newlines)
+  - source: generated by a simple shell script
+  - purpose: performance/regression test