travis.sh: Update sources before installing packages.
Merge pull request #1038 '[RDY] Update APT package sources in travis.sh.'
bugfix: set empty string as default for ipy/icpb to avoid segfault

Fixes #1039
Merge PR #1040 'Fix segfault caused by default value of ipy/icpb options'
Build deps on Travis: Use CMAKE_C_COMPILER_ARG1.

CMAKE_C_COMPILER_ARG1 is set in CMake toolchain file
cmake/i386-linux-gnu.toolchain.cmake. Use when compiling dependencies to
simplify 32-bit builds.