[snowball_ext, windows]: Fix the path to source/object files

Author: dmpgpro

contrib/snowball_ext/Makefile

@@ -7,8 +7,8 @@ PGFILEDESC = "snowball_ext - add-on dictionary template with natural language st
 
 REGRESS = snowball_ext
 ENCODING = UTF8
-OBJS= snowball_ext.o api.o utilities.o \
-	stem_UTF_8_nepali.o $(WIN32RES)
+OBJS= snowball_ext.o libstemmer/api.o libstemmer/utilities.o \
+	libstemmer/stem_UTF_8_nepali.o $(WIN32RES)
 
 SQLSCRIPT= snowball_ext--1.0.sql
 DATA_built = $(SQLSCRIPT)