[iOS] Prepare for upstreaming DumpRenderTree changes

https://bugs.webkit.org/show_bug.cgi?id=127412

Reviewed by Simon Fraser.

Unlike on Mac where DumpRenderTree is a command-line tool, on iOS it is
an application bundle. Instead of upstreaming a separate target for the
app that duplicates the 'Compile Sources' phase of the tool, separate
out the compilation into a static library target that both the
command-line tool and the app can link against. Also, perform some
unrelated cleanup.

* DumpRenderTree/DumpRenderTree.xcodeproj/project.pbxproj: Updated the
project file format from 2.4- to 3.2-compatible. Removed the
'Copy Headers' build phase and removed all files from the
'Compile Sources' build phase of DumpRenderTree. Added some files that
were missing from the project. Created a 'DumpRenderTree (Library)'
target for building the static library and made the 'DumpRenderTree'
target depend on it. Added a 'Compile Sources' build phase to this
target that builds the same files the DumpRenderTree target used to.
Created DumpRenderTreeMain.mm as the only source file of the
DumpRenderTree target, since targets won't link a binary without at
least one source file. Made DumpRenderTree (Library) use
DumpRenderTreeLibrary.xcconfig and made LayoutTestHelper use
BaseTarget.xcconfig (so that it doesn't try to link libDumpRenderTree.a).
* DumpRenderTree/mac/Configurations/BaseTarget.xcconfig: Moved
definitions of GCC_ENABLE_OBJC_EXCEPTIONS and GCC_PREFIX_HEADER from
DumpRenderTree.xcconfig to here so that LayoutTestHelper can use them.
* DumpRenderTree/mac/Configurations/DumpRenderTree.xcconfig: Passed
-force_load $(BUILT_PRODUCTS_DIR)libDumpRenderTree.a to OTHER_LDFLAGS.
This is needed to correctly link a static library containing an Objective-C
category (see <https://developer.apple.com/library/mac/qa/qa1490/_index.html>).
* DumpRenderTree/mac/Configurations/DumpRenderTreeLibrary.xcconfig: Added.
* DumpRenderTree/mac/DumpRenderTree.mm:
(DumpRenderTreeMain): Renamed from main.
* DumpRenderTree/mac/DumpRenderTreeMac.h: Added declaration of DumpRenderTreeMain.
* DumpRenderTree/mac/DumpRenderTreeMain.mm: Added.
(main): Called DumpRenderTreeMain from main.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162573 268f45cc-cd09-0410-ab3c-d52691b4dbfc