Fix libproxy usage.

Partially revert 30f9eb49

configure.ac

@@ -1736,7 +1736,19 @@ AM_CONDITIONAL(BUILD_HTTPD, [test "${enable_httpd}" != "no"])
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 dnl libproxy support
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-PKG_ENABLE_MODULES_VLC([LIBPROXY], [], [libproxy-1.0], [libproxy support], [auto])
+AC_ARG_ENABLE(libproxy,
+  [  --enable-libproxy       libproxy support (default auto)])
+AS_IF([test "${enable_libproxy}" != "no"], [
+  PKG_CHECK_MODULES(LIBPROXY, libproxy-1.0, [
+    AC_DEFINE(HAVE_LIBPROXY, 1, [Define if libproxy is available])
+    VLC_ADD_CFLAGS([access_http],[$LIBPROXY_CFLAGS])
+    VLC_ADD_LIBS([access_http],[$LIBPROXY_LIBS])
+  ], [
+    AS_IF([test "x${enable_libproxy}" != "x"], [
+      AC_MSG_ERROR([libproxy could not be found on your system])
+    ])
+  ])
+])
 
 
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