Add support for displaying the language in the frame-format string.

Enable ${language} to be specified in the frame-format string to see
the current frame's compile unit language in "frame info".

Test Plan:
debug a C++ program, run to main, and run the lldb commands:
    settings set frame-format "frame lang=${language}\n"
    frame info
you should see:
    frame lang=c++
test case added in:
    ./dotest.py --executable lldb -f SettingsCommandTestCase.test_set_frame_format
Reviewers: clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D10561

llvm-svn: 240440
diff --git a/lldb/test/settings/TestSettings.py b/lldb/test/settings/TestSettings.py
index 4305107..17d34b7 100644
--- a/lldb/test/settings/TestSettings.py
+++ b/lldb/test/settings/TestSettings.py
@@ -129,7 +129,7 @@
         self.format_string = m.group(1)
 
         # Change the default format to print function.name rather than function.name-with-args
-        format_string = "frame #${frame.index}: ${frame.pc}{ ${module.file.basename}`${function.name}{${function.pc-offset}}}{ at ${line.file.fullpath}:${line.number}}\n"
+        format_string = "frame #${frame.index}: ${frame.pc}{ ${module.file.basename}`${function.name}{${function.pc-offset}}}{ at ${line.file.fullpath}:${line.number}}{, lang=${language}}\n"
         self.runCmd("settings set frame-format %s" % format_string)
 
         # Immediately test the setting.