Start preparing release notes to 1.7.5

diff --git a/RelNotes b/RelNotes
index b942e499449d97aeb50c73ca2bdc1c6e6d528743..540b756d2f64d8c8ebf927a707b9b2cc0a4c6151 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.4.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.5.txt
\ No newline at end of file