Test failure on Linux

Start with libcodegen/File.h and tests.py, then reproduce test_codegen on Ubuntu and compare the generated code with the expected string. Trace the platform-dependent behavior around the reported include change; done means the test passes with the intended output on Linux and Windows.

After applying this patch:

--- a/libcodegen/File.h
+++ b/libcodegen/File.h
@@ -7,6 +7,7 @@
 #ifndef FILE_H
 #define FILE_H
 #include <string.h>
+#include <unistd.h>
 #ifdef _WIN32
 #include "win_unistd.h"
 #endif 

I've been able to compile this extension on Ubuntu.

Running the test fails the same as in my previous report on Windows platform:

F
======================================================================
FAIL: test_codegen (tests.EchoprintTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/klo/git/python-echoprint/tests.py", line 8, in test_codegen
    self.assertEqual(d['code'], 'eJydz7sNAzAIRdGV-GPGiQHvP0KcypVdpDnNFUIPANDhAdWL963AC7T_YbrSnjJMocwJo7Qy5FAELdcqtpBt6Ezu38I0r4MH7e-3iroTDooJAZO7LO2AWeszaBXyXt_anXgQlcBr_QIy12Qh')
AssertionError: 'eJyd0juuQyEMRdEp2cbYZjjgz_yHEKrHy1VCkWYVW0I6CAAAFX6G4sb9LMMNtBtMN3q_cV_V2g2U32n0FUusWpTsn0h1NukQooQjImzVPwiSn-0PlsIm1pe33K9S06QOOgjw0Q7YNMEEW7U1vRvGhMzBqmpTi2B23KNkjBg83YEOblrz0Q5WwV5jmWUsXct65YES9_T3dsC-ryO8mnwCPfZ2qsC2_1F6H2QH7jzw0Q4vGHW94A==' != 'eJydz7sNAzAIRdGV-GPGiQHvP0KcypVdpDnNFUIPANDhAdWL963AC7T_YbrSnjJMocwJo7Qy5FAELdcqtpBt6Ezu38I0r4MH7e-3iroTDooJAZO7LO2AWeszaBXyXt_anXgQlcBr_QIy12Qh'

----------------------------------------------------------------------
Ran 1 test in 0.105s

Can you please fix the bug?

Thanks