[Debugger:WAF] Fixed unevaluated ${#vars} in defines dict.

Images were not loaded, b'couse of getting defined
DBGPLUG_DATA_DIR  "${PKGDATADIR}/debugger".

+ Fixed misspeling for "pludin_datadir"
Merge pull request #79 from vkochan/debugger_waf_defines_fix

[Debugger:WAF] Fixed unevaluated ${#vars} in defines dict.