Implement and document prefix options with arbitrary values including an
= sign. This needed to support -DNAME=value options as pass-through in
llvmc.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18203 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/CommandLine.html b/docs/CommandLine.html
index 55f5484..4f749b7 100644
--- a/docs/CommandLine.html
+++ b/docs/CommandLine.html
@@ -1276,13 +1276,15 @@
 specifies that this option is used to capture "interpreter style" arguments.  See <a href="#cl::ConsumeAfter">this section for more information</a>.</li>
 
 <li><a name="cl::Prefix">The <b><tt>cl::Prefix</tt></b></a> modifier specifies
-that this option prefixes its value.  With 'Prefix' options, there is no equal
-sign that separates the value from the option name specified.  This is useful
-for processing odd arguments like '<tt>-lmalloc -L/usr/lib'</tt> in a linker
-tool.  Here, the '<tt>l</tt>' and '<tt>L</tt>' options are normal string (list)
-options, that have the <a href="#cl::Prefix">cl::Prefix</a> modifier added to
-allow the CommandLine library to recognize them.  Note that <a
-href="#cl::Prefix">cl::Prefix</a> options must not have the <a
+that this option prefixes its value.  With 'Prefix' options, the equal sign does
+not separate the value from the option name specified. Instead, the value is
+everything after the prefix, including any equal sign if present. This is useful
+for processing odd arguments like <tt>-lmalloc</tt> and <tt>-L/usr/lib</tt> in a
+linker tool or <tt>-DNAME=value</tt> in a compiler tool.   Here, the 
+'<tt>l</tt>', '<tt>D</tt>' and '<tt>L</tt>' options are normal string (or list)
+options, that have the <a href="#cl::Prefix">cl::Prefix</a> modifier added to 
+allow the CommandLine library to recognize them.  Note that 
+<a href="#cl::Prefix">cl::Prefix</a> options must not have the <a
 href="#cl::ValueDisallowed">cl::ValueDisallowed</a> modifier specified.</li>
 
 <li><a name="cl::Grouping">The <b><tt>cl::Grouping</tt></b></a> modifier is used