In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

Most extension allow only for a boolean value so the current behaviour of just sending the extension with a trueish value is fine. However, some extensions that we could eventually support (like "objectformat") have a string value. This is a preparatory step towards that. ok stsp@

Feature requested by naddy. ok naddy, who also suggested some tweaks that will arrive shortly

ok millert, naddy

ok millert

POSIX says the limits defined there are available from <limits.h>, which almost all affected source files already included anyway. ok millert stsp

ok stsp