Teach save_to_pcap to write PCap-NG files

The PCap-NG file format is used by default by Wireshark as of
Wireshark 1.8.0 (June 2012). The main advantages of PCap-NG for
capturing via Corelatus hardware are:

   - Each packet has information about which interface it came from.

   - The capture file can include information about where the capture
     came from. This allows us to add the address of the capturing
     hardware.

c/Makefile

@@ -55,12 +55,16 @@ ship: version.c
 
 version.c: $(headers)
 	@echo "#include \"gth_apilib.h\"" > $@
-	@echo "const char *git_head = \""$(repo_head)"\";" >> $@
-	@echo "const char *build_hostname = \""$(shell hostname)"\";" >> $@
+	@echo "const char git_head[] = \""$(repo_head)"\";" >> $@
+	@echo "const char build_hostname[] = \""$(shell hostname)"\";" >> $@
 
-%: %.c $(headers) $(common_c_files) version.c
+%: %.c $(headers)
+
+%: %.c $(common_c_files) version.c
 	$(CC) -Wall -g -o $@ $^ $(LIBS)
 
-%.exe: %.c $(headers) $(common_c_files) version.c
+%.exe: %.c $(headers)
+
+%.exe: %.c $(common_c_files) version.c
 	$(CC_WIN32) -Wall -o $@ $^ $(LIBS_WIN32)
 

c/gth_apilib.h

@@ -91,8 +91,8 @@ typedef struct {
 } GTH_api;
 
 // For embedding the version into the object file
-extern const char *git_head;
-extern const char *build_hostname;
+extern const char git_head[];
+extern const char build_hostname[];
 
 // Close an API connection to the GTH, cleanly.
 //