Replace *Escape with *EscapeList

Follow the change to blueprint to make *Escape take and return a string
and add *EscapeList that take and return slices of strings.  Fix up
a few places that were unnecessarily converting a string to a slice
and back to a string.

Test: m nothing
Change-Id: I3fa87de175522205f36544ef76aa2f04aef1b936
diff --git a/cc/compiler.go b/cc/compiler.go
index 0aee0bd..53a60c7 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -269,7 +269,7 @@
 	CheckBadCompilerFlags(ctx, "vendor.cflags", compiler.Properties.Target.Vendor.Cflags)
 	CheckBadCompilerFlags(ctx, "recovery.cflags", compiler.Properties.Target.Recovery.Cflags)
 
-	esc := proptools.NinjaAndShellEscape
+	esc := proptools.NinjaAndShellEscapeList
 
 	flags.CFlags = append(flags.CFlags, esc(compiler.Properties.Cflags)...)
 	flags.CppFlags = append(flags.CppFlags, esc(compiler.Properties.Cppflags)...)