Configure: Rewrite detection for Xft2 to properly use PKG_CONFIG macro

The goal is to use standard macros, which make code easier to maintain
(smaller, more consistent). We still keep the legacy "xfg-config" method
because we don't want to drop support for old hardware/software.

A side effect is the change in the name of the variables for the makefile,
but this goes in favour of consistency.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

WINGs/Makefile.am

@@ -12,7 +12,7 @@ lib_LTLIBRARIES = libWUtil.la libWINGs.la
 
 
 LDADD= libWUtil.la libWINGs.la $(top_builddir)/wrlib/libwraster.la @INTLIBS@
-libWINGs_la_LIBADD = libWUtil.la $(top_builddir)/wrlib/libwraster.la @XLIBS@ @XFTLIBS@ @FCLIBS@ @LIBM@ @PANGOLIBS@
+libWINGs_la_LIBADD = libWUtil.la $(top_builddir)/wrlib/libwraster.la @XLIBS@ @XFT_LIBS@ @FCLIBS@ @LIBM@ @PANGOLIBS@
 libWUtil_la_LIBADD = @LIBBSD@
 
 EXTRA_DIST = BUGS make-rgb Examples Extras Tests
@@ -92,7 +92,7 @@ AM_CFLAGS =
 AM_CPPFLAGS = -DRESOURCE_PATH=\"$(datadir)/WINGs\" \
 	 -I$(top_srcdir)/WINGs/WINGs -I$(top_builddir)/WINGs/WINGs \
 	 -I$(top_builddir)/wrlib -I$(top_srcdir)/src \
-	@XFTFLAGS@ @HEADER_SEARCH_PATH@
+	@XFT_CFLAGS@ @HEADER_SEARCH_PATH@
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = WINGs.pc WUtil.pc
@@ -106,7 +106,7 @@ WINGs.pc: Makefile
 	@echo 'Version: $(VERSION)' >> $@
 	@echo 'Requires: wrlib WUtil' >> $@
 	@echo 'Libs: $(lib_search_path) -lWINGs' >> $@
-	@echo 'Libs.private: $(XFTLIBS) $(PANGOLIBS) $(XLIBS) -lm $(INTLIBS)' >> $@
+	@echo 'Libs.private: $(XFT_LIBS) $(PANGOLIBS) $(XLIBS) -lm $(INTLIBS)' >> $@
 	@echo 'Cflags: $(inc_search_path)' >> $@
 
 WUtil.pc: Makefile