Introduce COMPILER(GCC_OR_CLANG) guard and make COMPILER(GCC) true only for GCC

Introduce COMPILER(GCC_OR_CLANG) guard and make COMPILER(GCC) true only for GCC
https://bugs.webkit.org/show_bug.cgi?id=146833

Reviewed by Alexey Proskuryakov.

Source/JavaScriptCore:

* assembler/ARM64Assembler.h:
* assembler/ARMAssembler.h:
(JSC::ARMAssembler::cacheFlush):
* assembler/MacroAssemblerARM.cpp:
(JSC::isVFPPresent):
* assembler/MacroAssemblerX86Common.h:
(JSC::MacroAssemblerX86Common::isSSE2Present):
* heap/MachineStackMarker.h:
* interpreter/StackVisitor.cpp: Removed redundant COMPILER(CLANG) guards.
(JSC::logF):
* jit/HostCallReturnValue.h:
* jit/JIT.h:
* jit/JITOperations.cpp:
* jit/JITStubsARM.h:
* jit/JITStubsARMv7.h:
* jit/JITStubsX86.h:
* jit/JITStubsX86Common.h:
* jit/JITStubsX86_64.h:
* jit/ThunkGenerators.cpp:
* runtime/JSExportMacros.h:
* runtime/MathCommon.h: Removed redundant COMPILER(CLANG) guard.
(JSC::clz32):

Source/WebCore:

* platform/graphics/cpu/arm/filters/FELightingNEON.cpp:
* platform/graphics/cpu/arm/filters/FELightingNEON.h:
* platform/graphics/filters/FELighting.cpp:
(WebCore::FELighting::platformApply):
* platform/network/efl/NetworkStateNotifierEfl.cpp:
(WebCore::NetworkStateNotifier::readSocketCallback):

Source/WTF:

* wtf/Assertions.cpp:
* wtf/Assertions.h: Removed redundant COMPILER(CLANG) guard.
* wtf/Atomics.cpp:
* wtf/Atomics.h:
(WTF::weakCompareAndSwap):
(WTF::compilerFence):
* wtf/Compiler.h:
 - Renamed COMPILER(GCC) to COMPILER(GCC_OR_CLANG), because it is true for both compiler.
 - Added COMPILER(GCC) which is true only for GCC.
 - Moved all GCC related stuff to one block and removed redundant guards accordingly.
 - Removed the unused default false definition of GCC_VERSION_AT_LEAST for non GCC compilers.
* wtf/ExportMacros.h:
* wtf/FastMalloc.h:
* wtf/Platform.h:
* wtf/StdLibExtras.h:
* wtf/Vector.h:
* wtf/text/ASCIIFastPath.h:
(WTF::copyLCharsFromUCharSource):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@187819 268f45cc-cd09-0410-ab3c-d52691b4dbfc