Replace instances of datadeps --> data_deps.

tools/gn/docs/language.md

 # GN Language and Operation
 
 [TOC]
 
 ## Introduction
 
 This page describes many of the language details and behaviors.
 
 ### Use the built-in help!
 
@@ skipping 499 matching lines @@
 # the default toolchain. Pick the right one according to the current CPU
 # architecture.
 if (target_cpu == "x64") {
   set_default_toolchain("//toolchains:64")
 } else if (target_cpu == "x86") {
   set_default_toolchain("//toolchains:32")
 }
 ```
 
 If a 64-bit target wants to depend on a 32-bit binary, it would specify
-a dependency using `datadeps` (data deps are like deps that are only
+a dependency using `data_deps` (data deps are like deps that are only
 needed at runtime and aren't linked, since you can't link a 32-bit and a
 64-bit library).
 
 ```
 executable("my_program") {
   ...
   if (target_cpu == "x64") {
     # The 64-bit build needs this 32-bit helper.
-    datadeps = [ ":helper(//toolchains:32)" ]
+    data_deps = [ ":helper(//toolchains:32)" ]
   }
 }
 
 if (target_cpu == "x86") {
   # Our helper library is only compiled in 32-bits.
   shared_library("helper") {
     ...
   }
 }
 ```
@@ skipping 185 matching lines @@
 settings which work a bit differently in Blaze. This is partially to
 make conversion from the existing GYP code easier, and the GYP
 constructs generally offer more fine-grained control (which is either
 good or bad, depending on the situation).
 
 GN also uses GYP names like "sources" instead of "srcs" since
 abbreviating this seems needlessly obscure, although it uses Blaze's
 "deps" since "dependencies" is so hard to type. Chromium also compiles
 multiple languages in one target so specifying the language type on the
 target name prefix was dropped (e.g. from `cc_library`).