Improve compiler compatibility (#743)

* fix returns

* use standard C headers

* struct/class mismatch

* explicit this in template

* switch variable scope

* C standard compliance

* & l-value

include/d/actor/d_a_bk.h

@@ -6,7 +6,7 @@
 #include "SSystem/SComponent/c_phase.h"
 #include "m_Do/m_Do_hostIO.h"
 
-class dPath;
+struct dPath;
 namespace daObj_Search { class Act_c; };
 struct br_s;
 

include/d/actor/d_a_wind_tag.h

@@ -8,7 +8,7 @@
 #include "m_Do/m_Do_ext.h"
 
 class JPABaseEmitter;
-class dPath;
+struct dPath;
 
 namespace daWindTag {
     static BOOL CheckCreateHeap(fopAc_ac_c*);

include/d/actor/d_a_ykgr.h

@@ -3,7 +3,7 @@
 
 #include "f_op/f_op_actor.h"
 
-class dPath;
+struct dPath;
 class JPABaseEmitter;
 class JPABaseParticle;