cpp: fix documentation wording for data members in GlobalVariables

Some had incorrect words, or were missing a word and the end period.
Make it match with the descriptions in CommonCommandOptions.java.

Add a short documentation comment to |restart_reason| field.

--
Change-Id: Iac802eb3ed4f72dfd402e85d2098a5616b40a9de
Reviewed-on: https://bazel-review.googlesource.com/3530
MOS_MIGRATED_REVID=121478703
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java b/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
index 68df6a7..fb521ae 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CommonCommandOptions.java
@@ -212,10 +212,12 @@
       help = "The time in ms the launcher spends before sending the request to the blaze server.")
   public long startupTime;
 
-  @Option(name = "extract_data_time",
-      defaultValue = "0",
-      category = "hidden",
-      help = "The time spend on extracting the new blaze version.")
+  @Option(
+    name = "extract_data_time",
+    defaultValue = "0",
+    category = "hidden",
+    help = "The time in ms spent on extracting the new blaze version."
+  )
   public long extractDataTime;
 
   @Option(name = "command_wait_time",