lib/tokenize: fix two compiler warnings about emtpy while loop

Fixes these warnings:
  lib/tokenize.cpp: In member function ‘bool Tokenizer::tokenize(std::istream&, const char*, const std::string&)’:
  lib/tokenize.cpp:1962: warning: suggest a space before ‘;’ or explicit braces around empty body in ‘while’ statement
  lib/tokenize.cpp: In member function ‘bool Tokenizer::tokenizeCondition(const std::string&)’:
  lib/tokenize.cpp:2174: warning: suggest a space before ‘;’ or explicit braces around empty body in ‘while’ statement

Signed-off-by: Stefan Naewe <stefan.naewe@googlemail.com>