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-3.6/utils/idna.c
+++ netsurf-3.6/utils/idna.c
@@ -26,7 +26,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <libutf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include "utils/errors.h"
 #include "utils/idna.h"
@@ -250,7 +250,7 @@
 		return NSERROR_NOMEM;
 	}
 
-	nfc_size = utf8proc_normalise(nfc_label, nfc_size,
+	nfc_size = utf8proc_normalize_utf32(nfc_label, nfc_size,
 		UTF8PROC_STABLE | UTF8PROC_COMPOSE);
 	if (nfc_size < 0) {
 		return NSERROR_NOMEM;
@@ -565,7 +565,7 @@
 	}
 
 	/* Perform NFC normalisation */
-	ucs4_len = utf8proc_normalise(ucs4, u_ucs4_len,
+	ucs4_len = utf8proc_normalize_utf32(ucs4, u_ucs4_len,
 		UTF8PROC_STABLE | UTF8PROC_COMPOSE);
 	if (ucs4_len < 0) {
 		free(ucs4);
--- netsurf-3.6/test/Makefile
+++ netsurf-3.6/test/Makefile
@@ -112,11 +112,11 @@
 		-D_XOPEN_SOURCE=600 \
 		-Itest -Iinclude -Icontent/handlers -Ifrontends -I. -I.. \
 		-Dnsgtk \
-		$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc libidn) \
+		$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils libidn) \
 		$(LIB_CFLAGS) \
 		$(COV_CFLAGS)
 
-TESTLDFLAGS := $(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc libidn) -lz \
+TESTLDFLAGS := $(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils libidn) -lz -lutf8proc \
 		$(LIB_LDFLAGS)\
 		$(COV_LDFLAGS)