Introduce `PS_Decoder' and `PS_Builder' which include all fields
from either Type 1 or CFF decoders/builders.
* include/freetype/internal/psaux.h (PS_Builder, PS_Decoder): New
structs.
* src/psaux/psobjs.c, src/psaux/psobjs.h: Add `PS_Builder'
functions.
* src/psaux/psdecode.c, src/psaux/psdecode.h: New files to hold
`PS_Decoder' initialization functions.
* src/psaux/psaux.c, src/psaux/Jamfile (_sources),
src/psaux/rules.mk (PSAUX_DRV_SRC): Updated.