Fixing code-gen of constants. Fixes #182 Removes workaround 58b6d1.
Forcing recent GCC versions to place CFA-initialized constants in writeable memory, so CFA initialization doesn't segfault when writing them. See the const-init test for specifics about recent GCC versions.
src/InitTweak/FixGlobalInit.cc: generating the attribute to control GCC's placement
libcfa/src/limits.* : removing workaround from 58b6d1, making these limits const again
tests//limits.* : commenting old test that uses the constants from licfa-limits, explaining what the test doesn't exercise
tests//const-init.* : new test of static constants, taken from #182, and comments explaining how to test this issue