[mapguide-internals] Code review for std::string on Linux and other Valgrind fixes

[Trevor Wekel]

Hi everyone,

I have attached a set of patch files to https://trac.osgeo.org/mapguide/ticket/1423 which seem to correct the std::string threading behaviour for GETTILEIMAGE.  My test case is fairly limited so there may be other areas of the code susceptible to std::string thread safety.

I will submit the changes to branches/2.2 and trunk once another developer has had a chance to look them over.  Since we are in release candidate mode, code review prior to submission is more appropriate.

Regards,
Trevor