[git] Set automatic line endings on all files.

Ensures native file endings on all platforms.

Should fix an issue where the GocadTSurface_Mesh_Test failed
on Windows as the reader cannot read .ts files on Windows
with Linux line endings.

.gitattributes

+# Set the default behavior, in case people don't have core.autocrlf set.
+* text=auto
+
 # Enable style checks on source files
 *.h   hooks.style=uncrustify
 *.cpp hooks.style=uncrustify