Use char const * const * for Session::run

Needed to embed newer version of Clara

Closes #1178
Closes #1031

include/internal/catch_session.cpp

@@ -165,7 +165,7 @@ namespace Catch {
                 << std::left << std::setw(16) << "version: " << libraryVersion() << std::endl;
     }
 
-    int Session::applyCommandLine( int argc, char* argv[] ) {
+    int Session::applyCommandLine( int argc, char const * const * argv ) {
         if( m_startupExceptions )
             return 1;