Fix 2 bugs in dictionary loading

* Silently skip dictionaries less than 8 bytes, unless using `ZSTD_dct_fullDict`.
  This changes the compressor, which silently skips dictionaries <= 8 bytes.
* Allow repcodes that are equal to the dictionary content size, since it is in bounds.

tests/fuzz/Makefile

@@ -74,7 +74,7 @@ FUZZ_TARGETS :=       \
 	dictionary_decompress \
 	zstd_frame_info \
 	simple_compress \
-	dict_loader
+	dictionary_loader
 
 all: $(FUZZ_TARGETS)