- G.f's G_DEBUG flag was being erased in blenkernel/intern/blender.c's
  setup_app_data:

G.f= bfd->globalf

// added a line above it to fix this:

if (G.f & G_DEBUG) bfd->globalf |=G_DEBUG;
G.f= bfd->globalf;

BPython:
- debug info now only shown if Blender is started with '-d' option
- added ~/.blender/scripts to modules sys.path
- added two new functions to Blender.sys: basename and splitext
- added doc for Blender.sys, updated other docs