Support QtCore

[vgvassilev]

Currently our Qt module depends on QtCore which is non modularized:

CXXRecordDecl 0x1474528 </cvmfs/sft.cern.ch/lcg/views/LCG_rootext20170508/x86_64-slc6-gcc62-opt/include/QtCore/qglobal.h:1658:1, line:1794:1> line:1658:21 in GQt.TGQt.h hidden class QSysInfo definition
|-also in GQt.TQtClientWidget.h
|-CXXRecordDecl 0x1474670 <col:1, col:21> col:21 in GQt.TGQt.h hidden implicit class QSysInfo
|-AccessSpecDecl 0x1474728 <line:1659:1, col:7> col:1 in GQt.TGQt.h public
|-EnumDecl 0x1474758 <line:1660:5, line:1662:5> line:1660:10 in GQt.TGQt.h hidden Sizes
| `-EnumConstantDecl 0x14748d8 <line:1661:9, col:38> col:9 in GQt.TGQt.h hidden WordSize 'enum QSysInfo::Sizes'
|   `-ImplicitCastExpr 0x1474920 <col:20, col:38> 'unsigned int' <IntegralCast>
|     `-ParenExpr 0x14748b0 <col:20, col:38> 'unsigned long'
|       `-BinaryOperator 0x1474888 <col:21, col:37> 'unsigned long' '<<'
|         |-UnaryExprOrTypeTraitExpr 0x1474848 <col:21, col:34> 'unsigned long' sizeof 'void *'
|         `-IntegerLiteral 0x1474868 <col:37> 'int' 3
`-EnumDecl 0x1474940 <line:1672:5, line:1685:5> line:1672:10 in GQt.TGQt.h hidden Endian
  |-EnumConstantDecl 0x1474a18 <line:1673:9> col:9 in GQt.TGQt.h hidden referenced BigEndian 'enum QSysInfo::Endian'
  |-EnumConstantDecl 0x1474a68 <line:1674:9> col:9 in GQt.TGQt.h hidden referenced LittleEndian 'enum QSysInfo::Endian'
  `-EnumConstantDecl 0x1474ae0 <line:1681:11, col:23> col:11 in GQt.TGQt.h hidden ByteOrder 'enum QSysInfo::Endian'
    `-ImplicitCastExpr 0x1474b28 <col:23> 'unsigned int' <IntegralCast>
      `-DeclRefExpr 0x1474ab0 <col:23> 'int' EnumConstant 0x1474a68 'LittleEndian' 'enum QSysInfo::Endian'