base: move crt0.h and elf.h to base/internal

Those headers remained unused outside the internal framework. So it is
better to remove them from the public API.

Issue #1832

repos/base-linux/src/base/process/process.cc

@@ -12,14 +12,14 @@
  */
 
 /* Genode includes */
-#include <base/elf.h>
 #include <base/env.h>
 #include <base/process.h>
 #include <base/printf.h>
 #include <linux_native_pd/client.h>
 
-/* framework-internal includes */
+/* base-internal includes */
 #include <linux_syscalls.h>
+#include <base/internal/elf.h>
 
 
 using namespace Genode;

repos/base-linux/src/lib/lx_hybrid/lx_hybrid.cc

@@ -11,7 +11,7 @@
  * under the terms of the GNU General Public License version 2.
  */
 
-#include <base/crt0.h>
+//#include <base/crt0.h>
 #include <base/printf.h>
 #include <linux_syscalls.h>
 #include <linux_cpu_session/linux_cpu_session.h>

repos/base-linux/src/test/lx_rmap/main.cc

@@ -14,14 +14,12 @@
 /* Genode includes */
 #include <base/printf.h>
 #include <base/env.h>
-#include <base/crt0.h>
 #include <base/sleep.h>
 #include <base/thread.h>
 #include <util/misc_math.h>
 #include <rm_session/connection.h>
 
 
-
 static void blob() __attribute__((used));
 static void blob()
 {