s-numeric?: Match the complete line.

(s-numeric? "z7") should return nil.  In the current version it
returns t as soon as a digit is in the string.

However (s-numeric? "7\nz") still returns t.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
s-*case?: Use character classes instead of range.

The built-in character classes [:upper:]/[:lower:] take non-ascii
characters into account.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Merge pull request #22 from ruediger/s-numeric

Fix regexp matching in s-numeric?,s-*case?