* Adding "CC ?= gcc" portability

* Adding "CC ?= gcc" portability
* Using -nc for all wget lines in order not to fetch files we've already fetched
* Changed the tar(1) lines, don't use "tar zxvf scim-tables-0.5.1.tar.gz > /dev/null",
  it's totally redundant, just skip the "v" option, also if you're going to get
  one file from a tarball "tar xzf ball.tar.gz -O file/i/want > want" is better
* Splitting "clean:" into "cleantmp:" and "cleandl:" to clean temporary files
  and files downloaded from the net respectively. kept using "make clean" will
  execute both of them.