Added a set of empty, classless 'extern "C"' probe functions to allow '.so' loaders and application domain 'autotools' to easily and unambiguously check for the correct installation of the various bullet libraries.

eg:

  bulletmath_suffix="-lbulletmath"
  bulletcollision_suffix="-lbulletcollision"
  bulletdynamics_suffix="-lbulletdynamics"
  dnl Check bulletmath library
  AC_CHECK_LIB(bulletmath, btBulletMathProbe, true,
  AC_MSG_ERROR([there seems to be a problem with the bulletmath library]))
  LIBS="$bulletmath_suffix $LIBS"
  dnl Check bulletcollision library
  AC_CHECK_LIB(bulletcollision, btBulletCollisionProbe, true,
  AC_MSG_ERROR([there seems to be a problem with the bulletcollision library]))
  LIBS="$bulletcollision_suffix $LIBS"
  dnl Check bulletdynamics library
  AC_CHECK_LIB(bulletdynamics, btBulletDynamicsProbe, true,
  AC_MSG_ERROR([there seems to be a problem with the bulletdynamics library]))
  LIBS="$bulletdynamics_suffix $LIBS"

src/LinearMath/btGeometryUtil.cpp

@@ -16,6 +16,15 @@ subject to the following restrictions:
 
 #include "btGeometryUtil.h"
 
+
+/*
+  Make sure this dummy function never changes so that it
+  can be used by probes that are checking whether the
+  library is actually installed.
+*/
+extern "C" void btBulletMathProbe () {}
+
+
 bool	btGeometryUtil::isPointInsidePlanes(const btAlignedObjectArray<btVector3>& planeEquations, const btVector3& point, btScalar	margin)
 {
 	int numbrushes = planeEquations.size();