vlc_fixups: protect sincos against macro substitution

It seems that it became a macro in some files on macosx now...

    ../../include/vlc_fixups.h:763:6: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/simd/math.h:2459:49: note: expanded from macro 'sincos'
    2459 | #define sincos(__x, __sinp, __cosp) __tg_sincos(__tg_promote1((__x))(__x), __sinp, __cosp)
    |                                                 ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/tgmath.h:60:39: note: expanded from macro '__tg_promote1'
    60 | #define __tg_promote1(__x)           (__typeof__(__tg_promote(__x)))
    |                                       ^
    In file included from ../../modules/gui/macosx/views/VLCSnowEffectView.m:25:
    In file included from ../../modules/gui/macosx/main/VLCMain.h:27:
    In file included from ../config.h:898:
    ../../include/vlc_fixups.h:763:6: error: function cannot return function type 'int (double)'
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/simd/math.h:2459:49: note: expanded from macro 'sincos'
    2459 | #define sincos(__x, __sinp, __cosp) __tg_sincos(__tg_promote1((__x))(__x), __sinp, __cosp)
    |                                                 ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/tgmath.h:60:38: note: expanded from macro '__tg_promote1'
    60 | #define __tg_promote1(__x)           (__typeof__(__tg_promote(__x)))
    |                                      ^
    3 errors generated.