Merging r309113:

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r309113 | yamaguchi | 2017-07-26 06:36:58 -0700 (Wed, 26 Jul 2017) | 19 lines

[Bash-autocompletion] Show HelpText with possible flags

Summary:
`clang --autocomplete=-std` will show
```
-std:   Language standard to compile for
-std=   Language standard to compile for
-stdlib=        C++ standard library to use
```
after this change.

However, showing HelpText with completion in bash seems super tricky, so
this feature will be used in other shells (fish, zsh...).

Reviewers: v.g.vassilev, teemperor, ruiu

Subscribers: cfe-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D35759
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@309437 91177308-0d34-0410-b5e6-96231b3b80d8

Author: zmodem

lib/Option/OptTable.cpp

@@ -235,7 +235,9 @@ OptTable::findByPrefix(StringRef Cur, unsigned short DisableFlags) const {
       continue;
 
     for (int I = 0; In.Prefixes[I]; I++) {
-      std::string S = std::string(In.Prefixes[I]) + std::string(In.Name);
+      std::string S = std::string(In.Prefixes[I]) + std::string(In.Name) + "\t";
+      if (In.HelpText)
+        S += In.HelpText;
       if (StringRef(S).startswith(Cur))
         Ret.push_back(S);
     }