lib/kernel-args: Store kernel args as key/value entries

Define an `OstreeKernelArgsEntry` structure, which holds
both the key and the value. The kargs order array stores
entries for each key/value pair, instead of just the keys.
The hash table is used to locate entries, by storing
entries in a pointer array for each key. The same public
interface is preserved, while maintaining ordering
information of each key/value pair when
appending/replacing/deleting kargs.

Fixes: #1859

src/libostree/ostree-kernel-args.h

@@ -27,11 +27,40 @@
 G_BEGIN_DECLS
 
 typedef struct _OstreeKernelArgs OstreeKernelArgs;
+typedef struct _OstreeKernelArgsEntry OstreeKernelArgsEntry;
 
 GHashTable *_ostree_kernel_arg_get_kargs_table (OstreeKernelArgs *kargs);
 
 GPtrArray *_ostree_kernel_arg_get_key_array (OstreeKernelArgs *kargs);
 
+char *
+_ostree_kernel_args_entry_get_key (const OstreeKernelArgsEntry *e);
+
+char *
+_ostree_kernel_args_entry_get_value (const OstreeKernelArgsEntry *e);
+
+void
+_ostree_kernel_args_entry_set_key (OstreeKernelArgsEntry *e,
+                                   char  *key);
+
+void
+_ostree_kernel_args_entry_set_value (OstreeKernelArgsEntry *e,
+                                     char  *value);
+
+char *
+_ostree_kernel_args_get_key_index (const OstreeKernelArgs *kargs,
+                                   int i);
+
+char *
+_ostree_kernel_args_get_value_index (const OstreeKernelArgs *kargs,
+                                     int i);
+
+OstreeKernelArgsEntry *
+_ostree_kernel_args_entry_new (void);
+
+void
+_ostree_kernel_args_entry_value_free (OstreeKernelArgsEntry *e);
+
 _OSTREE_PUBLIC
 void ostree_kernel_args_free (OstreeKernelArgs *kargs);