opencv: unbreak on big endian altivec builds

srcpkgs/opencv/patches/undef-altivec-macros-cpp.patch

@@ -0,0 +1,16 @@
+This is necessary because otherwise conflicts are introduced in C++ code that
+includes this. The header itself does not rely on the macros. The issue is not
+visible on little endian because they undef the macros somewhere else.
+
+--- 3rdparty/include/opencl/1.2/CL/cl_platform.h
++++ 3rdparty/include/opencl/1.2/CL/cl_platform.h
+@@ -332,6 +332,9 @@ typedef unsigned int cl_GLenum;
+ /* Define basic vector types */
+ #if defined( __VEC__ )
+    #include <altivec.h>   /* may be omitted depending on compiler. AltiVec spec provides no way to detect whether the header is required. */
++   #undef vector
++   #undef pixel
++   #undef bool
+    typedef __vector unsigned char     __cl_uchar16;
+    typedef __vector signed char       __cl_char16;
+    typedef __vector unsigned short    __cl_ushort8;