Use upstream utf8proc package, as suggested in
http://source.netsurf-browser.org/libutf8proc.git/commit/?id=770e329cceaf0620c7b482589a9b17ed1d19c16d

Work around upstream's lack of a pkg-config file and update API.

--- netsurf-3.6/Makefile
+++ netsurf-3.6/Makefile
@@ -527,10 +527,9 @@
 $(eval $(call pkg_config_find_and_add,libcss,CSS))
 $(eval $(call pkg_config_find_and_add,libdom,DOM))
 $(eval $(call pkg_config_find_and_add,libnsutils,nsutils))
-$(eval $(call pkg_config_find_and_add,libutf8proc,utf8proc))
 
 # Common libraries without pkg-config support
-LDFLAGS += -lz
+LDFLAGS += -lz -lutf8proc
 
 # Optional libraries with pkgconfig
 
--- netsurf-3.8/utils/idna.c
+++ netsurf-3.8/utils/idna.c
@@ -27,7 +27,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
-#include <libutf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include "netsurf/inttypes.h"
 
--- netsurf-3.8/test/Makefile
+++ netsurf-3.8/test/Makefile
@@ -142,14 +142,15 @@
 	-Itest -Iinclude -Icontent/handlers -Ifrontends -I. -I.. \
 	-Dnsgtk \
 	$(SAN_FLAGS) \
-	$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc) \
+	$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils) \
 	$(LIB_CFLAGS)
 TESTCFLAGS := $(BASE_TESTCFLAGS) \
 	$(COV_CFLAGS) \
 	$(COV_CPPFLAGS)
 
 TESTLDFLAGS := -L$(TESTROOT) \
-	$(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc) -lz \
+	$(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils) \
+	$(LDFLAGS) \
 	$(SAN_FLAGS) \
 	$(LIB_LDFLAGS)\
 	$(COV_LDFLAGS)
/services/syncthing.scm'>
<input type='hidden' name='id' value='c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad'>root</a>/<a href='/guix/log/gnu?id=c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad'>gnu</a>/<a href='/guix/log/gnu/services?id=c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad'>services</a>/<a href='/guix/log/gnu/services/syncthing.scm?id=c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad'>syncthing.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/syncthing.scm?id=c8f33b613e55322f0fc7dbdd72566aeb2f8f6dad&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-11-30 01:08:55 +0100'>2021-11-30</span></td><td><a href='/guix/commit/gnu/services/syncthing.scm?id=892f1b7273d57b25940700877a02618fe826cc08'>services: Accept &lt;inferior-package&gt;s in lieu of &lt;package&gt;s.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/authentication.scm (fprintd-configuration)
(nslcd-configuration): Substitute file-like objects for package ones.
* gnu/services/cgit.scm (cgit-configuration, opaque-cgit-configuration):
Likewise.
* gnu/services/cups.scm (package-list?, cups-configuration): Likewise.
* gnu/services/dns.scm (verify-knot-configuration)
(ddclient-configuration): Likewise.
* gnu/services/docker.scm (docker-configuration): Likewise.
* gnu/services/file-sharing.scm (transmission-daemon-configuration): Likewise.
* gnu/services/getmail.scm (getmail-configuration): Likewise.
* gnu/services/mail.scm (dovecot-configuration)
(opaque-dovecot-configuration): Likewise.
* gnu/services/messaging.scm (prosody-configuration)
(opaque-prosody-configuration): Likewise.
* gnu/services/monitoring.scm (zabbix-server-configuration)
(zabbix-agent-configuration): Likewise.
* gnu/services/networking.scm (opendht-configuration): Likewise.
* gnu/services/pm.scm (tlp-configuration): Likewise.
* gnu/services/telephony.scm (jami-configuration): Likewise.
* gnu/services/virtualization.scm (libvirt-configuration)
(qemu-guest-agent-configuration): Likewise.
* gnu/services/vpn.scm (openvpn-client-configuration): Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-01-12 14:40:36 +0300'>2021-01-12</span></td><td><a href='/guix/commit/gnu/services/syncthing.scm?id=79ba12a1dbb3e40b623dd0945a277f8720d9780a'>services: Add syncthing service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/syncthing.scm: New file.
* gnu/local.mk: Add this.
* doc/guix.texi: Document this.
</span></span></td><td>Oleg Pykhalov</td></tr>