[dmap] Use a wrapper for dmap_find_field()

Avoids the need to have definition of dmap_find_field in dmap_common.h that
must be kept in sync with the definition that gperf generates.

Also should fix compilation problems when gperf is not present, ref pr #390

src/dmap_common.c

@@ -42,6 +42,12 @@ dmap_get_fields_table(int *nfields)
   return dmap_fields;
 }
 
+// This wrapper is so callers don't need to include dmap_fields_hash.h
+const struct dmap_field *
+dmap_find_field_wrapper(const char *str, int len)
+{
+  return dmap_find_field(str, len);
+}
 
 void
 dmap_add_container(struct evbuffer *evbuf, const char *tag, int len)

src/dmap_common.h

@@ -2,7 +2,6 @@
 #ifndef __DMAP_HELPERS_H__
 #define __DMAP_HELPERS_H__
 
-#include "config.h"
 #include <event2/buffer.h>
 #include <event2/http.h>
 
@@ -45,9 +44,8 @@ extern const struct dmap_field_map dfm_dmap_aeSP;
 const struct dmap_field *
 dmap_get_fields_table(int *nfields);
 
-/* From dmap_fields.gperf - keep in sync, don't alter */
 const struct dmap_field *
-dmap_find_field (register const char *str, register GPERF_LEN_TYPE len);
+dmap_find_field_wrapper(const char *str, int len);
 
 
 void

src/httpd_daap.c

@@ -738,7 +738,7 @@ parse_meta(struct evhttp_request *req, char *tag, const char *param, const struc
 
       if (n == i)
 	{
-	  meta[i] = dmap_find_field(field, strlen(field));
+	  meta[i] = dmap_find_field_wrapper(field, strlen(field));
 
 	  if (!meta[i])
 	    {