Fix CheckIdentifierNotPurelyNumerical so it does not use IntFromString
Fix CheckIdentifierNotPurelyNumerical: return false/true not 0/1 and no single-line ifs
Merge pull request #610 from tzz/tzz/redmine-1193-purely-numerical-identifiers

Redmine#1193: Fix CheckIdentifierNotPurelyNumerical so it does not use IntFromString