C++ compilability: "not" is a C++ keyword, avoid it

see http://en.cppreference.com/w/cpp/language/operator_alternative

src/regcomp.c

@@ -1640,7 +1640,7 @@ compile_tree(Node* node, regex_t* reg)
 
       switch (NCTYPE(node)->ctype) {
       case ONIGENC_CTYPE_WORD:
-        if (NCTYPE(node)->not != 0)  op = OP_NOT_WORD;
+        if (NCTYPE(node)->is_not != 0)  op = OP_NOT_WORD;
         else                            op = OP_WORD;
         break;
       default:
@@ -2441,7 +2441,7 @@ is_not_included(Node* x, Node* y, regex_t* reg)
       switch (ytype) {
       case NT_CTYPE:
         if (NCTYPE(y)->ctype  == NCTYPE(x)->ctype &&
-            NCTYPE(y)->not   != NCTYPE(x)->not)
+            NCTYPE(y)->is_not != NCTYPE(x)->is_not)
           return 1;
         else
           return 0;
@@ -2473,7 +2473,7 @@ is_not_included(Node* x, Node* y, regex_t* reg)
       case NT_CTYPE:
         switch (NCTYPE(y)->ctype) {
         case ONIGENC_CTYPE_WORD:
-          if (NCTYPE(y)->not == 0) {
+          if (NCTYPE(y)->is_not == 0) {
             if (IS_NULL(xc->mbuf) && !IS_NCCLASS_NOT(xc)) {
               for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
                 if (BITSET_AT(xc->bs, i)) {
@@ -2550,9 +2550,9 @@ is_not_included(Node* x, Node* y, regex_t* reg)
         switch (NCTYPE(y)->ctype) {
         case ONIGENC_CTYPE_WORD:
           if (ONIGENC_IS_MBC_WORD(reg->enc, xs->s, xs->end))
-            return NCTYPE(y)->not;
+            return NCTYPE(y)->is_not;
           else
-            return !(NCTYPE(y)->not);
+            return !(NCTYPE(y)->is_not);
           break;
         default:
           break;
@@ -4668,7 +4668,7 @@ optimize_node_left(Node* node, NodeOptInfo* opt, OptEnv* env)
 
         switch (NCTYPE(node)->ctype) {
         case ONIGENC_CTYPE_WORD:
-          if (NCTYPE(node)->not != 0) {
+          if (NCTYPE(node)->is_not != 0) {
             for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
               if (! ONIGENC_IS_CODE_WORD(env->enc, i)) {
                 add_char_opt_map_info(&opt->map, (UChar )i, env->enc);
@@ -6170,7 +6170,7 @@ print_indent_tree(FILE* f, Node* node, int indent)
     fprintf(f, "<ctype:%x> ", (int )node);
     switch (NCTYPE(node)->ctype) {
     case ONIGENC_CTYPE_WORD:
-      if (NCTYPE(node)->not != 0)
+      if (NCTYPE(node)->is_not != 0)
         fputs("not word",       f);
       else
         fputs("word",           f);

src/regparse.h

@@ -247,7 +247,7 @@ typedef struct {
 typedef struct {
   NodeBase base;
   int ctype;
-  int not;
+  int is_not;
 } CtypeNode;
 
 typedef struct _Node {