[Autotools] Remove uses of Automake FARSTREAM_(CFLAGS|LIBS) variables, USE_FARSTREAM conditional
https://bugs.webkit.org/show_bug.cgi?id=109198

Reviewed by Martin Robinson.

.: 

* GNUmakefile.am: The USE_FARSTREAM conditional is being removed while the WTF_USE_FARSTREAM
define is currently a no-op.
* configure.ac: Don't set the Automake conditional as it's currently not needed due
to checking for Farstream dependency being removed in r142005.

Source/WebCore: 

* GNUmakefile.am: Remove FARSTREAM_CFLAGS variable, it's not set to anything.

Source/WebKit2: 

* GNUmakefile.am: Remove the FARSTREAM_(CFLAGS|LIBS) variables, they're
not set to anything.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142158 268f45cc-cd09-0410-ab3c-d52691b4dbfc