Add .gitattributes for test outputs

Marks test files as non-text in .gitattributes, to prevent line-ending
normalisation on them when checked out on Windows with autocrlf enabled.

Also, mark all .py files as lf-only, as this is what the parser expects (in
particular, for triple quoted strings).

Author: LeszekSwirski

.gitattributes

@@ -0,0 +1,9 @@
+# Mark python files as text ending with lf
+*.py             text eol=lf
+
+# Mark test outputs as non-text, to prevent line-ending normalization
+/test/**/*.expect         -text
+/test/**/*.trans          -text
+/test/**/*.py.symtab      -text
+/test/**/*.py.real        -text
+/test/**/*.py.real.alt    -text