This lets us use epicsParseDouble() for scan rate parsing.
Ensure the scanOnce thread is a higher priority than the fastest
periodic scan thread, irrespective of how many threads there are.
Adds new routines for converting numeric strings into the
standard epicsInt8, epicsUInt8, epicsInt16, epicsUInt16,
epicsInt32 and epicsUInt32 types, along with Long, ULong,
Double and Float. These all provide error checking and
detection of extraneous characters. The epicsScanDouble
and epicsScanFloat routines originally in epicsStdlib.h
are replaced by macros that call the epicsParse routine,
and this also provides epicsScanLong and epicsScanULong
to match.
A test file is added to ensure conversions work properly
and report appropriate errors. This file also checks the
native strtod() routine if not used to check whether the
epicsStrtod() code is required on this platform.
