[Qt] Make it possible to build WebKit without QtWidgets

[Qt] Make it possible to build WebKit without QtWidgets
https://bugs.webkit.org/show_bug.cgi?id=78109

Reviewed by Tor Arne Vestbø.

.:

* Source/QtWebKit.pro: Don't build WK1 tests and examples if WK1 is disabled.
* Source/api.pri: Move WK1 sources away from here and use WEBKIT += webkit1 instead
* WebKit.pro: Add WK1 to SUBDIRS unless no_webkit1 is set.

Source/WebKit:

Moved WebKit1 sources into a separate static library. Only WK1
depends on QtWidgets.

* WebKit1.pri: Added.
* WebKit1.pro: Added.

Source/WebKit2:

* WebKit2.pri: Add missing WK2 specific dependencies.
* qt/MainQt.cpp: Do the QStyle initialization hook only if we are
compiling with QtWidgets support.
(WebKit):
(main):

Tools:

* Tools.pro: Disable various tools that depend on WK1.
* qmake/mkspecs/features/default_post.prf: Add WK1 as supported static lib in WEBKIT
* qmake/mkspecs/features/default_pre.prf: Disable WK1 if QtWidgets is not built.
* qmake/mkspecs/modules/webkit1.prf: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121228 268f45cc-cd09-0410-ab3c-d52691b4dbfc