strings: Remove cmStdString references

Casts from std::string -> cmStdString were high on the list of things
taking up time. Avoid such implicit casts across function calls by just
using std::string everywhere.

The comment that the symbol name is too long is no longer relevant since
modern debuggers alias the templates anyways and the size is a
non-issue since the underlying methods are generated since it's
inherited.

Source/cmFindPathCommand.cxx

@@ -89,9 +89,9 @@ std::string
 cmFindPathCommand::FindHeaderInFramework(std::string const& file,
                                          std::string const& dir)
 {
-  cmStdString fileName = file;
-  cmStdString frameWorkName;
-  cmStdString::size_type pos = fileName.find("/");
+  std::string fileName = file;
+  std::string frameWorkName;
+  std::string::size_type pos = fileName.find("/");
   // if there is a / in the name try to find the header as a framework
   // For example bar/foo.h would look for:
   // bar.framework/Headers/foo.h
@@ -128,7 +128,7 @@ cmFindPathCommand::FindHeaderInFramework(std::string const& file,
     }
   // if it is not found yet or not a framework header, then do a glob search
   // for all frameworks in the directory: dir/*.framework/Headers/<file>
-  cmStdString glob = dir;
+  std::string glob = dir;
   glob += "*.framework/Headers/";
   glob += file;
   cmsys::Glob globIt;
@@ -136,7 +136,7 @@ cmFindPathCommand::FindHeaderInFramework(std::string const& file,
   std::vector<std::string> files = globIt.GetFiles();
   if(files.size())
     {
-    cmStdString fheader = cmSystemTools::CollapseFullPath(files[0].c_str());
+    std::string fheader = cmSystemTools::CollapseFullPath(files[0].c_str());
     if(this->IncludeFileInPath)
       {
       return fheader;