- Add BUILDING_SLIRP to the static library
- Ensure SLIRP_EXPORT is consistently used when defining an exported
  funcion
- Add some ISO C safety calls, e.g., strerror_s.
- Rabin-Karp string search algorithm for g_strstr_len. Needs a test
  harness to ensure that it works properly (hint: it does.)
- Add "WALL" option to CMakeLists.txt
- Add string operations test harness, strops_test.c
- Move tests under a tests/ subdirectory.
- Find and fix errata.
- Add <io.h> for Win32 POSIX-compatible functions, such as open(), close()
- Add slirp_os_socket typedef to abstract the network socket type.
  Unixen use int and Win32 uses SOCKET.
- inet_pton for non-Win32.