mercurial: force LF endings for *.py, *.{c,h} and *.t in .editorconfig

PyCharm on Windows otherwise uses CRLF.

Differential Revision: https://phab.mercurial-scm.org/D8947

.editorconfig

@@ -1,18 +1,21 b''
 # See http://EditorConfig.org for the specification
 
 root = true
 
 [*.py]
 indent_size = 4
 indent_style = space
 trim_trailing_whitespace = true
+end_of_line = lf
 
 [*.{c,h}]
 indent_size = 8
 indent_style = tab
 trim_trailing_whitespace = true
+end_of_line = lf
 
 [*.t]
 indent_size = 2
 indent_style = space
 trim_trailing_whitespace = false
+end_of_line = lf