Introduce nvim namespace: Move files.

Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

src/nvim/os/env.c

@@ -0,0 +1,80 @@
+// env.c -- environment variable access
+
+#include <uv.h>
+
+#include "os/os.h"
+#include "misc2.h"
+
+#ifdef HAVE__NSGETENVIRON
+#include <crt_externs.h>
+#endif
+
+#ifdef HAVE_SYS_UTSNAME_H
+#include <sys/utsname.h>
+#endif
+
+const char *os_getenv(const char *name)
+{
+  return getenv(name);
+}
+
+int os_setenv(const char *name, const char *value, int overwrite)
+{
+  return setenv(name, value, overwrite);
+}
+
+char *os_getenvname_at_index(size_t index)
+{
+# if defined(HAVE__NSGETENVIRON)
+  char **environ = *_NSGetEnviron();
+# elif !defined(__WIN32__)
+  // Borland C++ 5.2 has this in a header file.
+  extern char         **environ;
+# endif
+  // check if index is inside the environ array
+  for (size_t i = 0; i < index; i++) {
+    if (environ[i] == NULL) {
+      return NULL;
+    }
+  }
+  char *str = environ[index];
+  if (str == NULL) {
+    return NULL;
+  }
+  int namesize = 0;
+  while (str[namesize] != '=' && str[namesize] != NUL) {
+    namesize++;
+  }
+  char *name = (char *)vim_strnsave((char_u *)str, namesize);
+  return name;
+}
+
+
+int64_t os_get_pid()
+{
+#ifdef _WIN32
+  return (int64_t)GetCurrentProcessId();
+#else
+  return (int64_t)getpid();
+#endif
+}
+
+void os_get_hostname(char *hostname, size_t len)
+{
+#ifdef HAVE_SYS_UTSNAME_H
+  struct utsname vutsname;
+
+  if (uname(&vutsname) < 0) {
+    *hostname = '\0';
+  } else {
+    strncpy(hostname, vutsname.nodename, len - 1);
+    hostname[len - 1] = '\0';
+  }
+#else
+  // TODO(unknown): Implement this for windows.
+  // See the implementation used in vim:
+  // https://code.google.com/p/vim/source/browse/src/os_win32.c?r=6b69d8dde19e32909f4ee3a6337e6a2ecfbb6f72#2899
+  *hostname = '\0';
+#endif
+}
+