[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"
Fix typo to unbreak compilation on older GLib versions
Merge pull request #79 from vkochan/debugger_waf_defines_fix

[Debugger:WAF] Fixed unevaluated ${#vars} in defines dict.
Small fix at German translatation which caused a segfault on GeanySendMail if no mailer and/or filename placeholder has been configured