move elfparse includes to the module itself

The elfparse header doesn't require most of these includes, so don't
pull them in where they'll pollute other users of the header.  Instead
move all the headers elfparse.c needs to the source file itself.

Bug: None
Test: `make check` passes
Change-Id: I29377e900b42041f64f6229774ef7c872c74bce0
diff --git a/elfparse.c b/elfparse.c
index cd032af..4e74816 100644
--- a/elfparse.c
+++ b/elfparse.c
@@ -3,6 +3,13 @@
  * found in the LICENSE file.
  */
 
+#include <elf.h>
+#include <endian.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
 #include "elfparse.h"
 
 int is_elf_magic (const uint8_t *buf)