Fixed compilation error on RHEL 5.10.

Nesting the namespace "Internal" inside of other namespaces and using
sequential "using namespace" directives *or* relying on a "using
namespace" directive to resolve a method name that contained the
"Internal" namespace for resolution resulted in ambiguous resolution
errors when compiling with the RHEL5.10 stock compiler (GCC 4.1.2).  A
sample error is provided below:

Compilation error encountered was:
reference to 'Internal' is ambiguous
/usr/lib/gcc/x86_64-redhat-
candidates are: namespace Internal { }
qt-creator/src/libs/cplusplus/PPToken.h:106: error:
namespace CPlusPlus::Internal { }

Modifying the using namespace directives to reflect the nested nature of
the namespace names resolved the compilation errors.  For example:

using namespace CppEditor;
using namespace Internal;

produced errors.  However,

using namespace CppEditor;
using namespace CppEditor::Internal;

resolved the compilation errors by removing the ambiguity.

Change-Id: I6d5051e20acb2c147bd7ee1c6c6e1e3b2b4ff0f9
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/cplusplus/PPToken.cpp

@@ -32,6 +32,7 @@
 #include <cstring>
 
 using namespace CPlusPlus;
+using namespace CPlusPlus::Internal;
 
 bool ByteArrayRef::startsWith(const char *s) const
 {
@@ -52,7 +53,7 @@ int ByteArrayRef::count(char ch) const
     return num;
 }
 
-void Internal::PPToken::squeezeSource()
+void PPToken::squeezeSource()
 {
     if (hasSource()) {
         m_src = m_src.mid(offset, f.length);

src/plugins/cppeditor/cppelementevaluator.cpp

@@ -42,7 +42,7 @@
 #include <QQueue>
 
 using namespace CppEditor;
-using namespace Internal;
+using namespace CppEditor::Internal;
 using namespace CPlusPlus;
 
 namespace {

src/plugins/cppeditor/cppincludehierarchy.cpp

@@ -50,7 +50,7 @@
 #include <QVBoxLayout>
 
 using namespace CppEditor;
-using namespace Internal;
+using namespace CppEditor::Internal;
 using namespace Utils;
 
 namespace CppEditor {

src/plugins/cppeditor/cppsnippetprovider.cpp

@@ -42,7 +42,7 @@
 #include <QCoreApplication>
 
 using namespace CppEditor;
-using namespace Internal;
+using namespace CppEditor::Internal;
 
 CppSnippetProvider::CppSnippetProvider() :
     TextEditor::ISnippetProvider()

src/plugins/cppeditor/cpptypehierarchy.cpp

@@ -44,7 +44,7 @@
 #include <QLabel>
 
 using namespace CppEditor;
-using namespace Internal;
+using namespace CppEditor::Internal;
 using namespace Utils;
 
 namespace {