Remove the check on CC variable value because we have unittests now

And CC can be set to mpicc when 'usempi' is true, so this assertion is not
always correct.
Remove base classes that are already available via subtoolchains
Merge pull request #598 from gribozavr/clang-fixes

Assorted fixes for Clang toolchains
Remove useless sleep() calls that were slowing down Python scipy build
Add cgmvolf toolchain support
fixed default for --stop option'
Merge pull request #600 from gribozavr/cgmvolf-toolchain

Add cgmvolf toolchain support
Merge pull request #601 from JensTimmerman/fix_default_stop

fixed default for --stop option'
clarify comment
run proper unit test for run_cmd_qa
add longer run_cmd test
Merge pull request #5 from boegel/remove-useless-sleep

add/enhance unit tests, adjust comment
Merge pull request #599 from gribozavr/remove-useless-sleep

Remove useless (or undocumented) sleep() calls that were slowing down Python scipy build
Merge branch 'develop' of github.com:hpcugent/easybuild-framework into cuda_goolfc
simplify tests by focusing on CUDA aspects of goolfc, also test CUDA_CFLAGS and CUDA_CXXFLAGS
correctly define CUDA_CFLAGS and CUDA_CXXFLAGS without using update_variables hack
define CUDA_*FLAGS constants as FlagLists