Exclude (small) stack from RAM memory area (like on most other targets) to make expli...

Exclude (small) stack from RAM memory area (like on most other targets) to make explicit that the linker may not use all RAM. If the cc65 parameter stack isn't used at all the __STACKSIZE__ symbol may be overridden on the linker command line with -D __STACKSIZE__=0.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4820 b7a2c559-68d2-44c3-8de9-860c34a00d81