T2345: Replace instances of NULL with nullptr

The following changes have been applied to src and lib folders:
regex replace: ([^"_])NULL ⇒ \1nullptr (8968 chgs in src, 1153 in lib)
Manually find/change: (void \*) nullptr ⇒ nullptr (1 case)
regex find: ".*?nullptr.*?"
  Manually ~14 cases back to "NULL" in src, ~2 in lib
  regex finds a few false positive where nullptr appears between two
  strings in a function call

lib/atc/PaqAtcUtility.cpp

@@ -18,7 +18,7 @@ namespace ATC {
                                AtomType atomType) :
     atc_(atc),
     atomType_(atomType),
-    myNlocal(NULL)
+    myNlocal(nullptr)
   {
     switch (atomType_) {
       case ALL: