enable run tests on current build tree by command "builder buildtest"
reworked testenv.mif make file to switch path for compilers (exe and DLL), include path, run-time libraries DLLs
simplify make files by strict using extensions of source files for each compiler
*.gc, *.c for C compiler
*.gcp, *.cpp for C++ compiler
*.src for creating source code for c or c++
rename source files to to respect these rules