3748 zfs headers should be C++ compatible

*** 50,67 ****
  
  .KEEP_STATE:
  
  all: $(PROG)
  
! $(PROG): $(OBJS)
          $(LINK.c) -o $(PROG) $(OBJS) $(LDLIBS)
          $(POST_PROCESS)
  
  clean:
  
  lint:   lint_SRCS
  
  include ../../Makefile.targ
  
  %.o: ../%.c
          $(COMPILE.c) $<
          $(POST_PROCESS_O)
--- 50,75 ----
  
  .KEEP_STATE:
  
  all: $(PROG)
  
! $(PROG): $(OBJS) ztest_hdrck.o
          $(LINK.c) -o $(PROG) $(OBJS) $(LDLIBS)
          $(POST_PROCESS)
  
  clean:
+         $(RM) $(OBJS) ztest_hdrck.o
  
  lint:   lint_SRCS
  
  include ../../Makefile.targ
  
+ ztest_hdrck.cpp: ../ztest_hdrck.sh
+         ../ztest_hdrck.sh
+ 
+ %.o: %.cpp
+         $(COMPILE.cc) $<
+         $(POST_PROCESS_O)
+ 
  %.o: ../%.c
          $(COMPILE.c) $<
          $(POST_PROCESS_O)