Merge branch 'ab/deprecate-R-for-dynpath'

Merge branch 'ab/deprecate-R-for-dynpath'

The way of specifying the path to find dynamic libraries at runtime
has been simplified.  The old default to pass -R/path/to/dir has been
replaced with the new default to pass -Wl,-rpath,/path/to/dir,
which is the more recent GCC uses.  Those who need to build with an
old GCC can still use "CC_LD_DYNPATH=-R"

* ab/deprecate-R-for-dynpath:
  Makefile: remove the NO_R_TO_GCC_LINKER flag