fix Linux build

by default, only enable 64bit build when using ./premake4_linux64 and only 32bit build when using ./premake4_linux
remove some warning

build/premake4.lua

@@ -55,7 +55,16 @@ solution "0BulletSolution"
 	configuration "Debug"
 		flags { "Symbols", "StaticRuntime" , "NoMinimalRebuild", "NoEditAndContinue" ,"FloatFast"}
 		
-	platforms {"x32", "x64"}
+ if os.is("Linux") then
+                if os.is64bit() then
+                        platforms {"x64"}
+                else
+                        platforms {"x32"}
+                end
+        else
+                platforms {"x32", "x64"}
+        end
+
 	--platforms {"x32"}
 
   configuration {"Windows"}

src/BulletDynamics/ConstraintSolver/btTypedConstraint.h

@@ -414,7 +414,7 @@ struct	btTypedConstraintData
 	int		m_isEnabled;
 	
 };
-#endif BACKWARDS_COMPATIBLE
+#endif //BACKWARDS_COMPATIBLE
 
 struct	btTypedConstraintDoubleData
 {

src/LinearMath/btScalar.h

@@ -322,7 +322,24 @@ inline __m128 operator * (const __m128 A, const __m128 B)
 #define BT_INFINITY INFINITY
 #define BT_NAN NAN
 #endif//_WIN32
-#endif //BT_USE_SSE_IN_API
+#else
+
+#ifdef BT_USE_NEON
+	#include <arm_neon.h>
+
+	typedef float32x4_t btSimdFloat4;
+	#define BT_INFINITY INFINITY
+	#define BT_NAN NAN
+	#define btAssign128(r0,r1,r2,r3) (float32x4_t){r0,r1,r2,r3}
+#else//BT_USE_NEON
+
+	#ifndef BT_INFINITY
+	static  int btInfinityMask = 0x7F800000;
+	#define BT_INFINITY (*(float*)&btInfinityMask)
+	#endif
+#endif//BT_USE_NEON
+
+#endif //BT_USE_SSE
 
 #ifdef BT_USE_NEON
 #include <arm_neon.h>