initial commit fresh from tarball
mass consting and some XS efficiency tweaks

-remove "static const char *upperhex", this doesn't mean "0123456789ABCDEF"
 is static, but instead "char * upperhex" is static, and contains a
 pointer to "0123456789ABCDEF". Visual C doesn't optimize this extra
 variable away.
-replace multiple XPUSHs with 1 EXTEND and PUSHs, less calls to
 Perl_stack_grow(), in some cases, the incoming arg proves there is space
 on perl stack, so no EXTEND needed then
-replace MAX_DIV_16 with CPP constant so CC can optimizer better
-add const to all the tables, this allows the tables to be shared between
 perl processes on most OSes (including Win32) by the OS image loader
 saving 100s of KB of malloc-style per perl process memory