Fix compile warning being treated as error:

codec/svg.c: In function 'DecodeBlock':
codec/svg.c:240:5: error: implicit declaration of function 'rsvg_handle_render_cairo' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>

diff -uNr vlc-2.2.1.org/configure.ac vlc-2.2.1/configure.ac
--- vlc-2.2.1.org/configure.ac	2015-04-13 09:57:54.000000000 +0200
+++ vlc-2.2.1/configure.ac	2015-04-24 20:54:35.349039010 +0200
@@ -864,7 +864,7 @@
 dnl  Compiler warnings
 dnl
 
-RDC_PROG_CC_WFLAGS([all extra sign-compare undef pointer-arith bad-function-cast write-strings missing-prototypes volatile-register-var error-implicit-function-declaration])
+RDC_PROG_CC_WFLAGS([all extra sign-compare undef pointer-arith bad-function-cast write-strings missing-prototypes volatile-register-var])
 RDC_PROG_CC_FLAGS([-pipe])
 AC_LANG_PUSH([C++])
 RDC_PROG_CXX_WFLAGS([all extra sign-compare undef pointer-arith volatile-register-var])