[GTK] Clean up the TestWebKitAPI GNUmakefile.am
https://bugs.webkit.org/show_bug.cgi?id=115233

Reviewed by Martin Robinson.

Specify unconditional, non-installable program targets in one declaration. Only conditionally specify
WebKit2-specific targets, not the complete target setups (i.e. targets' sources, cppflags listings etc.).
Add missing unit test source files to the TestWTF program, namely HashSet.cpp and MetaAllocator.cpp.
Specify the TestWTF program's CXXFLAGS to be the same as the global cxxflags as the source files need to
be compiled with the -fno-rtti flag that's present in the global_cxxflags variable.

* TestWebKitAPI/GNUmakefile.am:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149195 268f45cc-cd09-0410-ab3c-d52691b4dbfc