Migrate source files into src/ directory

This change moves source files into a src/ directory,
and puts object files into an obj/ directory. The Makefile
and xcode project are updated accordingly.

Fixes #1866

src/wcstringutil.cpp

@@ -0,0 +1,40 @@
+/** \file wcstringutil.cpp
+
+Helper functions for working with wcstring
+*/
+
+#include "config.h"
+
+#include "wcstringutil.h"
+
+typedef wcstring::size_type size_type;
+
+wcstring_range wcstring_tok(wcstring& str, const wcstring &needle, wcstring_range last)
+{
+    size_type pos = last.second == wcstring::npos ? wcstring::npos : last.first;
+    if (pos != wcstring::npos && last.second != wcstring::npos) pos += last.second;
+    if (pos != wcstring::npos && pos != 0) ++pos;
+    if (pos == wcstring::npos || pos >= str.size())
+    {
+        return std::make_pair(wcstring::npos, wcstring::npos);
+    }
+
+    if (needle.empty())
+    {
+        return std::make_pair(pos, wcstring::npos);
+    }
+
+    pos = str.find_first_not_of(needle, pos);
+    if (pos == wcstring::npos) return std::make_pair(wcstring::npos, wcstring::npos);
+
+    size_type next_pos = str.find_first_of(needle, pos);
+    if (next_pos == wcstring::npos)
+    {
+        return std::make_pair(pos, wcstring::npos);
+    }
+    else
+    {
+        str[next_pos] = L'\0';
+        return std::make_pair(pos, next_pos - pos);
+    }
+}