fixed bootstrapping using sciteco-minimal and bootstrap autodetection

was broken due to untested changes
fixed buffer Ring initialization

 * there was a dependency on interface initialization.
   it did not cause issues because destruction order was
   by chance.
 * introduced INIT_PRIO and PRIO_* macros to easy initialization order declaration
   (using a PRIO_* formula makes code self-documenting)
 * also used this to clean up QRegisterTable initialization
   (we do not need the explicit initialize() method)
 * also used to clean up symbols initialization
perform additional expansions on explicitly-specified Scintilla paths

a common ./configure parameter would be --with-scintilla=~/scintilla.
however the calling shell will not expand tilde and the invoked
shell will not automatically fully expand variables.