Merge pull request #226 from chrox/master

matrix build using gcc and clang on Travis
add _DEFAULT_SOURCE define for czmq for newer glibc
Merge pull request #227 from hwhw/master

add _DEFAULT_SOURCE define for czmq for newer glibc
remove obsolete gettext fetch script
fix bug for "adding" color values

This is used for blitting with a per-blit alpha value. In 4bpp
mode, there was an error caused by improper use of the full byte
rather than just a nibble.
Merge pull request #228 from hwhw/master

Fix addblitFrom / alpha-blitting, remove unused download script
fix sdcv error 'GLIBCXX_3.4.15' not found
It seems that when environment variable `CXX` is defined the `AM_CXXFLAGS`
is ignored. This patch adds `-static-libstdc++` directly in `LDFLAGS` so
that sdcv need not to link libstdc++.so at run time.