Compiler compatibility (#1171)

* mark functions with duplicate names as static

* make std::__tag_va_List work with other compilers

* fix some offset comments

* use inlines in J3DJointFactory, JUTCacheFont

* fix class/struct mismatch

* improve const correctness

* fix missing return values

* make some JAudio namespaces more explicit

include/SSystem/SComponent/c_bg_s.h

@@ -10,7 +10,7 @@ class cBgS_ShdwDraw;
 class cBgS_LinChk;
 class cBgS_GndChk;
 class cM3dGPla;
-class cXyz;
+struct cXyz;
 
 class cBgS_ChkElm {
 public:

include/SSystem/SComponent/c_m3d.h

@@ -14,7 +14,7 @@ class cM3dGPla;
 class cM3dGSph;
 class cM3dGTri;
 class csXyz;
-class cXyz;
+struct cXyz;
 
 struct Vec;