Code Cleanup

- Cmake was not updating HAVE_ST_BIRTHTIME.
- NIBBLER_FEATURE_DATE was not properly applied everywhere.
- FEATURE_COLOR was not properly set.
- Some source files failed to include cmake.h, and therefore were not properly
- Removed inefficient use of std::string::substr for guaranteed single character
  strings.
- Integrated Directory::cd.
- Integrated File::ctime, ::btime.
- Integrated Path::operator+.
- Integrated Nibbler::getDigit{2,4,6}.
- Integrated HighResTimer.
  enabling/disabling code.
- All Path objects now expanded internally to absolute form.
- Modified unit tests to accomodate absolute paths.
- Merged new nibbler.t.cpp tests.
- Made various methods const.
- Includes removed from some files, added to others.

src/File.cpp

@@ -32,6 +32,7 @@
 #include <unistd.h>
 #include <File.h>
 #include <text.h>
+#include <cmake.h>
 #include <util.h>
 #include <i18n.h>
 
@@ -101,7 +102,7 @@ bool File::create ()
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-bool File::remove ()
+bool File::remove () const
 {
   return unlink (_data.c_str ()) == 0 ? true : false;
 }
@@ -335,6 +336,30 @@ time_t File::mtime () const
   return 0;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+time_t File::ctime () const
+{
+  struct stat s;
+  if (!stat (_data.c_str (), &s))
+    return s.st_ctime;
+
+  return 0;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+time_t File::btime () const
+{
+  struct stat s;
+  if (!stat (_data.c_str (), &s))
+#ifdef HAVE_ST_BIRTHTIME
+    return s.st_birthtime;
+#else
+    return s.st_ctime;
+#endif
+
+  return 0;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 bool File::create (const std::string& name)
 {