consider both lib64 and lib subdirs for GCC
add support for extra compilers on the side, which use prefixed compiler variables (e.g. CUDA_CC), add support for updating compiler variables (e.g. to use  to complete value for prefixed compiler variables like CUDA_CC), add and handle LIB_RUNTIME
add constant for CUDA compilers
support templated list-like values in option map
add support for updating compiler variables (e.g. to use  to complete value for prefixed compiler variables like CUDA_CC)
extend toolchain unit tests for comp_family and CUDA-enabled toolchain
add test modules required for goolfc unit test
add toolchain definitions for CUDA compiler, and gcccuda and goolfc compiler toolchains
code style fixes
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
Merge branch 'develop' into cuda_goolfc
Merge branch 'unit_testing' into cuda_goolfc
include goolfc 1.3.12 test module (+ deps) instead of goolfc 1.4.10 (CUDA doesn't play well with GCC 4.7)
fixed remarks
Merge branch 'develop' into cuda_goolfc
don't define compiler family as GCCCUDA, main compiler is still GCC
define 'prefixes' class variable, and make necessary adjustments to use it; move initialising of compiler options to set_options, adjust unit test accordingly