one more STEP

• build fixes
  • dependency fixes for expparse / expscan.
  • handle newer clang compilers
  • more robust parallel building
• relocation of headers and explicit directory prefixes
  • client codes should now include one directory (for example, /usr/include/stepcode) and specify headers in their code using path/header.h - (for example, #include <clstepcore/sdai.h>)
  • previous releases required explicit listing of all stepcode folders due to internal header include directives - this has been corrected