Add .gitattributes

Add the good default options as recommended by GitHub.
Helps to work around issues when using hybrid environments like
the Bash On Windows (see #4228).

.gitattributes

@@ -0,0 +1,15 @@
+# Set the default behavior, in case people don't have core.autocrlf set.
+#* text=auto # Does it cause problems on OSX?
+
+# Explicitly declare text files you want to always be normalized and converted
+# to native line endings on checkout.
+*.cpp text
+*.hpp text
+
+# Declare files that will always have CRLF line endings on checkout.
+*.bat text eol=crlf
+*.cmd text eol=crlf
+*.ps1 text eol=crlf
+
+# Declare files that will always have LF line endings on checkout.
+*.sh text eol=lf