MK_ARB_EABI was removed in r272350 so remove the documentation.
Per r273155, HYPERV is built by default on platforms where it makes
sense and ignored on others.
Document that WITHOUT_TOOLCHAIN causes headers to not be installed, not
just programs.
Regenerate src.conf.5 after:

r273170:
  MK_ARB_EABI was removed in r272350 so remove the documentation.
r273171:
  Per r273155, HYPERV is built by default on platforms where it makes
  sense and ignored on others.
r273172:
  Document that WITHOUT_TOOLCHAIN causes headers to not be installed, not
  just programs.