Move garray_T from structs.h to garray.h

src/garray.h

@@ -1,6 +1,21 @@
 #ifndef NEOVIM_GARRAY_H
 #define NEOVIM_GARRAY_H
 
+/*
+ * Structure used for growing arrays.
+ * This is used to store information that only grows, is deleted all at
+ * once, and needs to be accessed by index.  See ga_clear() and ga_grow().
+ */
+typedef struct growarray {
+  int ga_len;                       /* current number of items used */
+  int ga_maxlen;                    /* maximum number of items possible */
+  int ga_itemsize;                  /* sizeof(item) */
+  int ga_growsize;                  /* number of items to grow each time */
+  void    *ga_data;                 /* pointer to the first item */
+} garray_T;
+
+#define GA_EMPTY    {0, 0, 0, 0, NULL}
+
 void ga_clear(garray_T *gap);
 void ga_clear_strings(garray_T *gap);
 void ga_init(garray_T *gap);