C89/Visual C compatible

Note, some GCC platforms have broken alloca functions and require
"#define _alloca(size) __builtin_alloca(size)" . A non constant length auto
array is implemented with alloca in C99 under the hood. The other problems
were mixed declarations and statements.
lexical scope avoidence optimizations
Merge branch 'master' of https://github.com/bulk88/Text--Levenshtein--Damerau--XS