tclap depends upon config.h and the HAVE_CONFIG_H macro for proper behavior. The current implementation has a couple of problems:
* config.h isn't installed along with the rest of tclap, so unless the project using tclap defines HAVE_CONFIG_H and has a config.h which defines the appropriate macros tclap will not be fully functional.
* Arg.h and ValuesConstrant.h assume that if HAVE_CONFIG_H is defined then HAVE_SSTREAM or HAVE_STRSTREAM are also defined. In the case where a project defines HAVE_CONFIG_H but doesn't define either of the other two the compilation fails because no stream header is included.
To remedy this I've made the following changes:
* config/config.h is installed as tclap/config.h
* PACKAGE specific macros are removed from config.h to avoid clashing with those defined by other packages
* the HAVE_CONFIG_H guards (and any dependent stream logic) are removed and tclap/config.h is unconditionally included