devel/bullet: unbreak on 9.x

In file included from src/BulletInverseDynamics/IDConfig.hpp:65,

from src/BulletInverseDynamics/IDMath.hpp:6,
from src/BulletInverseDynamics/IDMath.cpp:1:

src/BulletInverseDynamics/details/IDLinearMathInterface.hpp: In constructor 'btInverseDynamicsBullet3::vecx::vecx(int)':
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:51: error: class 'btInverseDynamicsBullet3::vecx' does not have any field named 'btVectorX'
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp: In member function 'const btInverseDynamicsBullet3::vecx& btInverseDynamicsBullet3::vecx::operator=(const btVectorX<float>&)':
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: expected type-specifier before 'btVectorX'
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: expected `>' before 'btVectorX'
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: expected `(' before 'btVectorX'
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: missing template arguments before '*' token
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: expected primary-expression before '>' token
src/BulletInverseDynamics/details/IDLinearMathInterface.hpp:53: error: expected `)' before ';' token

Reported by: pkg-fallout
Approved by: portmgr blanket