Fixed an interpreter problem where an indirect store through an
ArgX parameter was incorrectly applying the "implicit conversion
rules" during the store.  From the ACPI specification: "If the
target is a method local or argument (LocalX or ArgX), no
conversion is performed and the result is stored directly to the
target".  The new behavior is to disable implicit conversion
during ALL stores to an ArgX.

Changed the behavior of the _PRW method scan to ignore any and
all errors returned by a given _PRW.  This prevents the scan from
aborting from the failure of any single _PRW.

Moved the runtime configuration parameters from the global init
procedure to static variables in acglobal.h.  This will allow the
host to override the default values easily.