pci: Fix wrong offsets of PCI configuration

Fix wrong offsets which cause boot from IDE fail.

It's probably also causing a PCI class code related issue stated in the
previous discussion:

  https://groups.google.com/d/msg/osv-dev/BU4P54xHSdU/p4_2EbOgXaQJ

Fixes #362.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Chenyi Lee <konya.vic@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: Fix pthread_getattr_np()

pthread_getattr_np should initialize the "attr" provided. It is not
pre-initialized.

Fixes the following boot-time crash:

  [penberg@localhost osv]$ ./scripts/run.py
  OSv v0.10-223-gd1ec5ce
  eth0: 192.168.122.15
  page fault outside application, addr: 0x0000000053bd2000
  [registers]
  RIP: 0x00000000003a84e0 <pagecache::access_scanner::access_scanner()+4032>
  RFL: 0x0000000000010246  CS:  0x0000000000000008  SS:  0x0000000000000010
  RAX: 0xffff800000de1008  RBX: 0x0000000053bd2000  RCX: 0xffff800000de1001  RDX: 0x0000000000000000
  RSI: 0x0000000000000000  RDI: 0x0000000053bd2000  RBP: 0x00002000003ff990  R8:  0x0000000000000000
  R9:  0xffffa0003bd4bebf  R10: 0xffffa0003f953fb0  R11: 0x00005fffffbfe000  R12: 0x00002000003ffb80
  R13: 0xffffa0003bd4bebf  R14: 0xffffa0003f953fb0  R15: 0x00005fffffbfe000  RSP: 0x00002000003ff980
  Aborted

  [backtrace]
  0x000000000032233f <mmu::jvm_balloon_vma::split(unsigned long)+367>
  0x0000000000323142 <mmu::vm_fault(unsigned long, exception_frame*)+146>
  0x000000000036f519 <page_fault+105>
  0x000000000036e406 <ex_pf+34>
  0x00000000003a885d <pagecache::access_scanner::access_scanner()+4925>
  0x00000000003ab897 <free+87>
  0x000000000041e5b6 <pthread_attr_destroy+22>
  0x00001000013db1a6 <JVM_handle_linux_signal+3798>
  0x00001000013db27c <JVM_handle_linux_signal+4012>
  0x0000100001507097 <JVM_handle_linux_signal+1232327>
  0x000010000150d691 <JVM_handle_linux_signal+1258433>
  0x0000100001210246 <JNI_CreateJavaVM+102>
  0x00001000008091ab <mkoption(std::string)+1067>
  0x0000100000809808 <mkoption(std::string)+2696>
  0x000000000047ecef <execute_native_thread_routine+31>
  0x00000000003b9f5a <thread_main_c+26>
  0x000000000036f385 <thread_main+7>
  0x087b8d48a8758aff <???+-1468691713>
  0x00000000003ba46f <sched::thread::~thread()+815>
  0x48ec834853fc8948 <???+1409059144>
  QEMU: Terminated

Signed-off-by: Calle Wilund <calle@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Http Server: File System DF RESTful API

This adds df information based on statfs api. The API provides the block
usage and node usage. Sample exexcution: http://127.0.0.1:8000/fs/df/

Signed-off-by: Shlomi Livne <shlomi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>