Handle trailing spaces on "settings set" command more correctly

Summary:
Currently we have some settings which treat "\ " on settings set commands specially. E.g., it is
a valid way of specifying an argument of " " to a target. However, this fails if "\ " is the last
argument as CommandObjectSettingsSet strips trailing whitespace. This resulted in a surprising
argument of "\" to the target.

This patch disables the training whitespace removal at a global
level. Instead, for each argument type we locally determine whether whitespace stripping makes
sense. Currently, I strip whitespace for all simple object type except of regex and
format-string, with the rationale that these two object types do their own complex parsing and we
want to interfere with them as least as possible. Specifically, stripping the whitespace of a
regex "\ " will result in a (surprising?) error "trailing backslash". Furthermore, the default
value of dissasembly-format setting already contains a trailing space and there is no way for the
user to type this in manually if we strip whitespace.

Reviewers: clayborg, zturner

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D7592

llvm-svn: 229382
diff --git a/lldb/source/Interpreter/OptionValueArch.cpp b/lldb/source/Interpreter/OptionValueArch.cpp
index 7df1492..eae903c 100644
--- a/lldb/source/Interpreter/OptionValueArch.cpp
+++ b/lldb/source/Interpreter/OptionValueArch.cpp
@@ -55,8 +55,10 @@
         
     case eVarSetOperationReplace:
     case eVarSetOperationAssign:
-        if (value_cstr && value_cstr[0])
+        if (value_cstr)
         {
+            std::string value = llvm::StringRef(value_cstr).trim().str();
+            value_cstr = value.c_str();
             if (m_current_value.SetTriple (value_cstr))
             {
                 m_value_was_set = true;