avcodec/jpegtables: Mark jpegtables as hidden

These tables are not exported as avpriv symbols, but instead
included into every library using them. Therefore they
can be mark with the hidden elf visibility. For certain arches
this is necessary in order to avoid building suboptimal code;
for other arches it just allows the compiler to simplify accesses
like ff_mjpeg_bits_dc_luminance + 1 because the "+ 1" can be baked
into the offset.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/jpegtables.h

@@ -23,6 +23,9 @@
 
 #include <stdint.h>
 
+#include "libavutil/attributes_internal.h"
+
+FF_VISIBILITY_PUSH_HIDDEN
 extern const uint8_t ff_mjpeg_bits_dc_luminance[];
 extern const uint8_t ff_mjpeg_val_dc[];
 
@@ -33,5 +36,6 @@ extern const uint8_t ff_mjpeg_val_ac_luminance[];
 
 extern const uint8_t ff_mjpeg_bits_ac_chrominance[];
 extern const uint8_t ff_mjpeg_val_ac_chrominance[];
+FF_VISIBILITY_POP_HIDDEN
 
 #endif /* AVCODEC_JPEGTABLES_H */