sigscheme: new package in lang section

sigscheme: new package in lang section

this patch adds a new package in the lang section:

http://code.google.com/p/sigscheme/

SigScheme is a R5RS Scheme interpreter for embedded use. It features
small footprint (64KB in library form on the 'small' configuration)
like SIOD and TinyScheme, low memory consumption (2-words per cons
cell), multibyte characters handling (UTF-8, EUCs and Shift_JIS) and
more.

-Raphael

git-svn-id: svn://svn.openwrt.org/openwrt/packages@21473 3c298f89-4303-0410-b956-a3cf2f4a3e73