fix _FILE_OFFSET_BITS redefined warning on Solaris/i386 platform

Summary:
The problem with Solaris is that system header files include
/usr/include/sys/feature_tests.h header file and it tests if
_FILE_OFFSET_BITS define is defined. If not, it defines it to 32
which is in conflict with 64 which we need for large file support.
The solution is easy, always include own header files before system header
files.

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D644

(cherry picked from commit 78216e22)