CppTools: set default -std=c++11 for Qt4

qmake from Qt4 does not provide C++ standard and
clang can't properly compile Qt4.8.6 and earlier
with c++1z. Behavior in this commit mimics qmake
from Qt5 which also provides c++11 as a default
standard.

Task-number: QTCREATORBUG-16441
Change-Id: I3d29891d6e47f2367f2b3b2bf4be4d86661924e9
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cpptools/cppcodemodelinspectordumper.cpp

@@ -144,7 +144,8 @@ QString Utils::toString(ProjectPart::QtVersion qtVersion)
     switch (qtVersion) {
     CASE_QTVERSION(UnknownQt);
     CASE_QTVERSION(NoQt);
-    CASE_QTVERSION(Qt4);
+    CASE_QTVERSION(Qt4_8_6AndOlder);
+    CASE_QTVERSION(Qt4Latest);
     CASE_QTVERSION(Qt5);
     // no default to get a compiler warning if anything is added
     }

src/plugins/cpptools/cppprojectinfogenerator.cpp

@@ -205,12 +205,15 @@ void ProjectInfoGenerator::createProjectParts(const RawProjectPart &rawProjectPa
         const ProjectPart::Ptr part = projectPartFromRawProjectPart(rawProjectPart,
                                                                     m_projectUpdateInfo.project);
 
+        ProjectPart::LanguageVersion defaultVersion = ProjectPart::LatestCxxVersion;
+        if (rawProjectPart.qtVersion == ProjectPart::Qt4_8_6AndOlder)
+            defaultVersion = ProjectPart::CXX11;
         if (cat.hasCxxSources()) {
             createProjectPart(rawProjectPart,
                               part,
                               cat.cxxSources(),
                               cat.partName("C++"),
-                              ProjectPart::LatestCxxVersion,
+                              defaultVersion,
                               ProjectPart::NoExtensions);
         }
 
@@ -219,7 +222,7 @@ void ProjectInfoGenerator::createProjectParts(const RawProjectPart &rawProjectPa
                               part,
                               cat.objcxxSources(),
                               cat.partName("Obj-C++"),
-                              ProjectPart::LatestCxxVersion,
+                              defaultVersion,
                               ProjectPart::ObjectiveCExtensions);
         }
 

src/plugins/cpptools/projectpart.h

@@ -80,7 +80,8 @@ public:
     enum QtVersion {
         UnknownQt = -1,
         NoQt,
-        Qt4,
+        Qt4_8_6AndOlder,
+        Qt4Latest,
         Qt5
     };