Several warnings detected by static code analyzer fixed
Implicit type conversion argument of function to size_t type
Suspicious sequence of types castings: size_t -> int -> size_t
Consider reviewing the expression of the 'A = B == C' kind. The expression is calculated as following: 'A = (B == C)'
Unsigned type is never < 0
Add POSIX regex sources when needed
Windows doesn't support POSIX regex, so we need to include it
ourselves. The sources come from git, which in turn took them from
gawk.