Version 0.13.1 Minor updates

blocktest.fth

• fixed issue #7 faults with single buffer blocks

core.fth

• corrected ACCEPT buffer block length to decimal 80 characters

coreplustest.fth

• moved double number with prefixes to doubletest.fth
• now tests maximum length definition names and all graphical characters accepted
• parses upper case characters using 'X' notation
• tests FIND with zero length strings and non-existent names

doubletest.fth

• received double number with prefixes from coreplus.fth