schemas FEATURE add schema getters from the context

Also check for the duplicities in the context when parsing a new schema.
diff --git a/src/parser_yang.c b/src/parser_yang.c
index 434073d..7ea75c6 100644
--- a/src/parser_yang.c
+++ b/src/parser_yang.c
@@ -1424,7 +1424,7 @@
         return LY_EVALID;
     }
 
-    strncpy(rev->rev, word, word_len);
+    strncpy(rev->date, word, word_len);
     free(buf);
 
     YANG_READ_SUBSTMT_FOR(ctx, data, kw, word, word_len, ret) {