Refactor the 'TRX Burst Interface' block

The following changes were made:

  - Both implementation and headers were merged with misc_utils
  - Fixed namespace mess: was gr::grgsm, became gr::gsm
  - More accurate class name was chosen: "trx_burst_if"
diff --git a/grc/misc_utils/CMakeLists.txt b/grc/misc_utils/CMakeLists.txt
index adb90d3..9407caf 100644
--- a/grc/misc_utils/CMakeLists.txt
+++ b/grc/misc_utils/CMakeLists.txt
@@ -31,6 +31,7 @@
     gsm_burst_file_source.xml
     gsm_message_file_sink.xml
     gsm_message_file_source.xml
+    gsm_trx_burst_if.xml
     gsm_msg_to_tag.xml
     gsm_controlled_fractional_resampler_cc.xml DESTINATION share/gnuradio/grc/blocks
 )