argument: Clean up argv types to match standard definitions

Change-Id: Idabdaac7b7a3879d6a2e18e46df986a1543df48f
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/argument.cpp b/argument.cpp
index 8931969..ed74a9d 100644
--- a/argument.cpp
+++ b/argument.cpp
@@ -39,7 +39,7 @@
     { 0, 0, 0, 0},
 };
 
-ArgumentParser::ArgumentParser(int argc, char** argv)
+ArgumentParser::ArgumentParser(int argc, char * const argv[])
 {
     int option = 0;
 
@@ -83,7 +83,7 @@
     }
 }
 
-void ArgumentParser::usage(char** argv)
+void ArgumentParser::usage(char * const argv[])
 {
     std::cerr << "Usage: " << argv[0] << " options\n";
     std::cerr << "Options:\n";