Remove our local modifications to sqlite's os_unix.c now that

third_party/sqlite/README.chromium

 Name: SQLite
 License File: src/LICENSE
 URL: http://sqlite.org/
 
 Instructions for importing a new release of SQLite from sqlite.org.
 
 Note: our current base version is 3.6.18.
 
 First, you need to be on Linux.
 
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  - fts2_icu.c and fts3_icu.c have a critical bug. U8_NEXT is used over
    a UTF-16 string. It's rep$ by U16_NEXT (jungshik)
  - Added a new function sqlite3Preload we use to prime the database cache. It
    allows much faster performance by reading the file in one contiguous
    operation rather than bringing it in organically, which involves a lot of
    seeking. This change also required sqlite3PcacheGetCachesize to be compiled
    even outside SQLITE_TEST.
  - Added a new function chromium_sqlite3_initialize_win_sqlite3_file()
    at the end of os_win.c. It allows the Windows-specific Chromium VFS
    to reuse most of the win32 SQLite VFS.
- - Added a new function
-   chromium_sqlite3_initialize_unix_sqlite3_file() and made
-   fillInUnixFile() non-static in os_unix.c. It allows the
-   Linux-specific Chromium VFS to reuse most of the unix SQLite VFS.
- - Exposed three functions that deal with unused file descriptors in
-   os_unix.c, to allow Chromium's Posix VFS implementation in
-   WebKit/WebCore/platform/sql/chromium/SQLiteFileSystemChromiumPosix.cpp
-   to correctly implement the "unused file descriptors" logic in the
-   xDlOpen() method. The new functions are
-   chromium_sqlite3_get_reusable_file_handle(),
-   chromium_sqlite3_update_reusable_file_handle() and
-   chromium_sqlite3_destroy_reusable_file_handle(). Also, added the
-   chromium_sqlite3_fill_in_unix_sqlite3_file() function that calls
-   fillInUnixFile(), which will be made static again as soon as a
-   WebKit patch using the new function lands.