update to GMT6

src/gridding.cpp

@@ -3,6 +3,8 @@
 #include "string"
 #include "unistd.h"
 
+#define GMT_VF_LEN 16
+
 int main(int argc, char *argv[])
 {
 	std::string table_name = "../data/table.txt";

src/plot_grid.cpp

@@ -4,6 +4,8 @@
 #include "iostream"
 #include "string"
 
+#define GMT_VF_LEN 16
+
 int main(int argc, char *argv[])
 {
 	std::string cpt_file = "../data/ex2.cpt";

src/plot_memory.cpp

@@ -4,6 +4,8 @@
 #include "iostream"
 #include "string"
 
+#define GMT_VF_LEN 16
+
 int main(int argc, char *argv[])
 {
 	std::string cpt_file = "../data/ex3.cpt";