Fix depfile parser test case line continuation
Fix depfile parser test case line continuation

Escape newlines for line continuation in the SpecialChars test case.
Otherwise the test does not cover valid Makefile syntax.  The missing
line continuation was tolerated by our parser but is never (not)
produced by a real compiler.

Qix-/ninja,martine/ninja,sgraham/ninja,AoD314/ninja,mydongistiny/ninja,ninja-build/ninja,atetubou/ninja,ndsol/subninja,mydongistiny/ninja,bradking/ninja,AoD314/ninja,martine/ninja,sgraham/ninja,iwadon/ninja,iwadon/ninja,maruel/ninja,maruel/ninja,nicolasdespres/ninja,atetubou/ninja,ninja-build/ninja,ndsol/subninja,iwadon/ninja,sgraham/ninja,ndsol/subninja,martine/ninja,mydongistiny/ninja,maruel/ninja,ninja-build/ninja,bradking/ninja,Qix-/ninja,Qix-/ninja,mydongistiny/ninja,AoD314/ninja,iwadon/ninja,ninja-build/ninja,martine/ninja,atetubou/ninja,bradking/ninja,AoD314/ninja,maruel/ninja,nicolasdespres/ninja,sgraham/ninja,atetubou/ninja,nicolasdespres/ninja,bradking/ninja,nicolasdespres/ninja,Qix-/ninja,ndsol/subninja