Add support for pread64/pwrite64

64-bit pread() and pwrite() is needed for ZipFileRO to be able to read
ludicrously large ZIP files just in case someone is crazy enough to do
it.

Also fix a license header that was apparently mangled.

Change-Id: I6819ef8b36e46b63b40749c95717b1ecf9307033
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 38e2825..aa236bd 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -133,7 +133,9 @@
 extern ssize_t read(int, void *, size_t);
 extern ssize_t write(int, const void *, size_t);
 extern ssize_t pread(int, void *, size_t, off_t);
+extern ssize_t pread64(int, void *, size_t, off64_t);
 extern ssize_t pwrite(int, const void *, size_t, off_t);
+extern ssize_t pwrite64(int, const void *, size_t, off64_t);
 
 extern int dup(int);
 extern int dup2(int, int);