GL: update the --magnum-log option to include "verbose".

src/Magnum/GL/Context.cpp

@@ -457,7 +457,7 @@ Context::Context(NoCreateT, Utility::Arguments& args, Int argc, const char** arg
     args.addOption("disable-workarounds")
         .setHelp("disable-workarounds", "driver workarounds to disable\n      (see http://doc.magnum.graphics/magnum/opengl-workarounds.html for detailed info)", "LIST")
         .addOption("disable-extensions").setHelp("disable-extensions", "OpenGL extensions to disable", "LIST")
-        .addOption("log", "default").setHelp("log", "Console logging", "default|quiet")
+        .addOption("log", "default").setHelp("log", "console logging", "default|quiet|verbose")
         .setFromEnvironment("disable-workarounds")
         .setFromEnvironment("disable-extensions")
         .setFromEnvironment("log")

src/Magnum/GL/Context.h

@@ -120,7 +120,8 @@ either from the `Platform::*Application` classes or from the
 
 @code{.sh}
 <application> [--magnum-help] [--magnum-disable-workarounds LIST]
-              [--magnum-disable-extensions LIST] ...
+              [--magnum-disable-extensions LIST]
+              [--magnum-log default|quiet|verbose] ...
 @endcode
 
 Arguments:
@@ -131,6 +132,8 @@ Arguments:
     @ref opengl-workarounds for detailed info) (environment: `MAGNUM_DISABLE_WORKAROUNDS`)
 -   `--magnum-disable-extensions LIST` --- OpenGL extensions to disable
     (environment: `MAGNUM_DISABLE_EXTENSIONS`)
+-   `--magnum-log default|quiet|verbose` --- console logging
+    (environment: `MAGNUM_LOG`) (default: `default`)
 
 Note that all options are prefixed with `--magnum-` to avoid conflicts with
 options passed to the application itself. Options that don't have this prefix