Portability

Manually include unistd.h in a couple of places get things building with gcc
4.7, which removed it from the global namespace. This fixes the following build
errors:

    src/A3.cpp:283:3: error: 'STDIN_FILENO' was not declared in this scope
    src/commands/CmdEdit.cpp:598:30: error: 'getpid' was not declared in this scope
    src/commands/CmdEdit.cpp:603:47: error: 'chdir' was not declared in this scope

Signed-off-by: Paul Beckingham <paul@beckingham.net>

src/A3.cpp

@@ -31,6 +31,7 @@
 #include <sstream>
 #include <algorithm>
 #include <stdlib.h>
+#include <unistd.h>
 #include <sys/select.h>
 #include <Context.h>
 #include <Directory.h>

src/commands/CmdEdit.cpp

@@ -30,6 +30,7 @@
 #include <iostream>
 #include <sstream>
 #include <stdlib.h>
+#include <unistd.h>
 #include <Duration.h>
 #include <Context.h>
 #include <i18n.h>