Use the EGL pkgconfig for finding eglplatform.h.

We don't ever explicity link against libEGL, so no need to make use of
EGL_LIBS.

Fixes #30.

configure.ac

@@ -98,6 +98,7 @@ AC_SUBST(EPOXY_LINK_LIBS)
 
 AM_CONDITIONAL(BUILD_EGL, test x$build_egl = xyes)
 if test x$build_egl = xyes; then
+    PKG_CHECK_MODULES(EGL, [egl])
     AC_DEFINE([BUILD_EGL], [1], [build EGL tests])
 fi
 

src/Makefile.am

@@ -28,6 +28,7 @@ AM_CFLAGS = \
 	$(CWARNFLAGS) \
 	$(VISIBILITY_CFLAGS) \
 	$(X11_CFLAGS) \
+	$(EGL_CFLAGS) \
 	$()
 
 epoxyincludedir = $(includedir)/epoxy

test/Makefile.am

@@ -46,7 +46,9 @@ libwgl_common_la_LIBADD = $(EPOXY)
 AM_CPPFLAGS = \
 	-I$(top_srcdir)/include \
 	-I$(top_builddir)/include \
-	$(X11_CFLAGS)
+	$(X11_CFLAGS) \
+	$(EGL_CFLAGS) \
+	$()
 
 AM_CFLAGS = $(CWARNFLAGS)