Add a --help (-h) option to "command script add" that enables users to define a one-liner short help for their command

Also, in case they don't define any, change the default from "Run Python function <blah>" into "For more information run help <blah>"

The core issue here is that Python only allows one docstring per function, so we can't really attach both a short and a long help to the same command easily
There are alternatives but this is not a pressing enough concern to go through the motions quite yet

Fixes rdar://18322737

llvm-svn: 217795
diff --git a/lldb/source/Interpreter/CommandObject.cpp b/lldb/source/Interpreter/CommandObject.cpp
index 3fdbf99..d8eade8 100644
--- a/lldb/source/Interpreter/CommandObject.cpp
+++ b/lldb/source/Interpreter/CommandObject.cpp
@@ -1103,6 +1103,7 @@
     { eArgTypeFunctionName, "function-name", CommandCompletions::eNoCompletion, { nullptr, false }, "The name of a function." },
     { eArgTypeFunctionOrSymbol, "function-or-symbol", CommandCompletions::eNoCompletion, { nullptr, false }, "The name of a function or symbol." },
     { eArgTypeGDBFormat, "gdb-format", CommandCompletions::eNoCompletion, { GDBFormatHelpTextCallback, true }, nullptr },
+    { eArgTypeHelpText, "help-text", CommandCompletions::eNoCompletion, { nullptr, false }, "Text to be used as help for some other entity in LLDB" },
     { eArgTypeIndex, "index", CommandCompletions::eNoCompletion, { nullptr, false }, "An index into a list." },
     { eArgTypeLanguage, "language", CommandCompletions::eNoCompletion, { LanguageTypeHelpTextCallback, true }, nullptr },
     { eArgTypeLineNum, "linenum", CommandCompletions::eNoCompletion, { nullptr, false }, "Line number in a source file." },