[gcr: 1/2] Update README to mention correct environment variables

[Daiki Ueno <dueno src gnome org>]

commit e1c73b3596b29632627cf2998594741e826b746e
Author: Dmitry Eremin-Solenikov <dbaryshkov gmail com>
Date:   Thu Oct 24 01:24:03 2019 +0300

    Update README to mention correct environment variables
    
    Use G_MESSAGES_DEBUG instead of non-working GCR_DEBUG/GCK_DEBUG.
    
    Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov gmail com>

 README | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)
---
diff --git a/README b/README
index 77993d6..af148d4 100644
--- a/README
+++ b/README
@@ -12,32 +12,22 @@ DEBUG TRACING
 The Gcr and Gck libraries contain statements which help debug flow
 and logic. In many cases these help you track down problems.
 
-Use the environment variable GCR_DEBUG='all' or GCR_HELP='xxx' to
-display either all messages or a specific category of debug messages.
-To figure out what you can use in place of the 'xxx' category above,
-use GCR_DEBUG='help' and you'll see a list of all the messages.
+Use the environment variable G_DEBUG_MESSAGES='all' or G_DEBUG_MESSAGES='xxx'
+to display either all messages or a specific categories of debug messages. You
+can separate categories in this list with spaces, commas or semicolons. Gcr
+library uses category 'Gcr', while Gck library uses category 'Gck'.
 
 Example to display all debug messages:
 
- $ GCR_DEBUG=all gcr-viewer /path/to/certificate.crt
+ $ G_DEBUG_MESSAGES=all gcr-viewer /path/to/certificate.crt
  (gcr-viewer:9418): Gcr-DEBUG: gcr_pkcs11_initialize_async: starting initialize of registered modules
  ...
 
-Example to display the various debug categories:
-
- $ GCR_DEBUG=help gcr-viewer /path/to/certificate.crt
- Supported debug values: library certificate-chain parse gnupg trust import key prompt all help
-
 Example to display debug messages for a specific category:
 
- $ GCR_DEBUG=library gcr-viewer /path/to/certificate.crt
+ $ G_DEBUG_MESSAGES="Gcr" gcr-viewer /path/to/certificate.crt
  (gcr-viewer:9503): Gcr-DEBUG: gcr_pkcs11_initialize_async: starting initialize of registered modules
  ...
 
-If you wish to permanently enable certain debug messages, include compiler
-directives like this when configuring this library:
-
- $ CFLAGS='-DGCR_DEBUG=library' ./configure ...
-
-For the Gck debug messages simply replace 'GCR_DEBUG' with 'GCK_DEBUG'
-in the above examples.
+For the Gck debug messages simply replace 'Gcr' with 'Gck' in the above
+examples.