Rewrite _hadd in assembler (a huge speedup!) and integrate it with free

for even faster code. The old _hadd function is now also written in
assembler but does only setup variables and calls the internal function
that is part of free.


git-svn-id: svn://svn.cc65.org/cc65/trunk@182 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/.cvsignore

@@ -25,7 +25,6 @@ vsprintf.s
 sprintf.s
 abort.s
 errormsg.s
-_hadd.s
 cprintf.s
 vcprintf.s
 freopen.s