Add SALOME 6.4.0 Release Notes

diff --git a/SALOME_6_3_1_Release_Notes.pdf b/SALOME_6_3_1_Release_Notes.pdf
deleted file mode 100755 (executable)
index 8234cc6..0000000
Binary files a/SALOME_6_3_1_Release_Notes.pdf and /dev/null differ

diff --git a/SALOME_6_4_0_Release_Notes.pdf b/SALOME_6_4_0_Release_Notes.pdf
new file mode 100755 (executable)
index 0000000..425f439
Binary files /dev/null and b/SALOME_6_4_0_Release_Notes.pdf differ