Replace WTF::getCurrentLocalTime() with GregorianDateTime::setToCurrentLocalTime()

Replace WTF::getCurrentLocalTime() with GregorianDateTime::setToCurrentLocalTime()
https://bugs.webkit.org/show_bug.cgi?id=92286

Reviewed by Geoffrey Garen.

Add a method to GregorianDateTime to set its values to the current locale time.
Replacing all occurrences of getCurrentLocalTime with the new function allows
us to remove getCurrentLocalTime in a next step.

Source/JavaScriptCore:

* JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore.def:

Source/WebCore:

* html/FTPDirectoryDocument.cpp:
(WebCore::processFileDateString):
* loader/archive/mhtml/MHTMLArchive.cpp:
(WebCore::MHTMLArchive::generateMHTMLData):

Source/WTF:

* GNUmakefile.list.am:
* WTF.gypi:
* WTF.pro:
* WTF.vcproj/WTF.vcproj:
* WTF.xcodeproj/project.pbxproj:
* wtf/CMakeLists.txt:
* wtf/DateMath.cpp:
(WTF::dayInYear):
* wtf/DateMath.h:
(WTF):
* wtf/GregorianDateTime.cpp: Added.
(WTF):
(WTF::GregorianDateTime::setToCurrentLocalTime):
* wtf/GregorianDateTime.h:
(GregorianDateTime):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@124365 268f45cc-cd09-0410-ab3c-d52691b4dbfc