Move hoehrmann to src to support out-of-tree builds more easily

without changing the include path

.gitmodules

 [submodule "hoehrmann-utf8"]
-	path = hoehrmann-utf8
+	path = src/hoehrmann-utf8
 	url = https://git.sr.ht/~slink/hoehrmann-utf8

src/Makefile.am

@@ -7,6 +7,7 @@ vmod_LTLIBRARIES = \
 
 libvmod_j_la_LDFLAGS = $(VMOD_LDFLAGS)
 libvmod_j_la_SOURCES = \
+	hoehrmann-utf8/src/hoehrmann-utf8.h \
 	vsbjson.c \
 	vsbjson.h \
 	vmod_j.c
@@ -25,6 +26,7 @@ vsbjson_test_CFLAGS = $(AM_CFLAGS)
 vsbjson_test_LDFLAGS = $(VARNISHAPI_LIBS)
 
 vsbjson_test_SOURCES = \
+	hoehrmann-utf8/src/hoehrmann-utf8.h \
 	vsbjson.c \
 	vsbjson.h \
 	vsbjson-test.c
@@ -46,6 +48,8 @@ TESTS = \
 
 # Documentation
 
+EXTRA_DIST = hoehrmann-utf8/LICENSE
+
 dist_doc_DATA = \
 	vmod_j.vcc \
 	$(TESTS)