be/c: fix code being generated for effect detected not to be used

[michaellilltokiwa]

some code like if(effectenv->fzEnvInstalled<effNum>) was generated despite effect with effNum never being used.
This is due to effect.type.is_installed being used but not replace/default/abort etc.
The c compiler then complained about this:

/tmp/fuzion_test_process_13769855200547668566.c:134351:41: error: no member named 'fzEnvInstalled_28359' in 'struct fzThrd_effectsEnvironment'
        if (!fzThrd_effectsEnvironment->fzEnvInstalled_28359)
             ~~~~~~~~~~~~~~~~~~~~~~~~~  ^
/tmp/fuzion_test_process_13769855200547668566.c:142548:34: error: no member named 'fzEnvInstalled_27995' in 'struct fzThrd_effectsEnvironment'; did you mean 'fzEnvInstalled_27977'?
  if (fzThrd_effectsEnvironment->fzEnvInstalled_27995)
                                 ^~~~~~~~~~~~~~~~~~~~
                                 fzEnvInstalled_27977
/tmp/fuzion_test_process_13769855200547668566.c:81219:8: note: 'fzEnvInstalled_27977' declared here
  bool fzEnvInstalled_27977;
       ^
/tmp/fuzion_test_process_13769855200547668566.c:142971:37: error: no member named 'fzEnvInstalled_27995' in 'struct fzThrd_effectsEnvironment'; did you mean 'fzEnvInstalled_27977'?
    if (!fzThrd_effectsEnvironment->fzEnvInstalled_27995)
                                    ^~~~~~~~~~~~~~~~~~~~
                                    fzEnvInstalled_27977
/tmp/fuzion_test_process_13769855200547668566.c:81219:8: note: 'fzEnvInstalled_27977' declared here
  bool fzEnvInstalled_27977;
       ^
3 errors generated.

error 1: C backend: C compiler failed
C compiler call 'clang --target=x86_64-pc-linux-gnu -ftrapv -Wall -Werror -Wextra -Wpedantic -Wformat=2 -Wno-unused-parameter -Wshadow -Wwrite-strings -Wold-style-definition -Wredundant-decls -Wnested-externs -Wmissing-include-dirs -Wno-strict-prototypes -Wno-gnu-empty-initializer -Wno-zero-length-array -Wno-trigraphs -Wno-gnu-empty-struct -Wno-unused-variable -Wno-unused-label -Wno-unused-function -Wno-pointer-to-int-cast -Wno-infinite-recursion -Wno-unused-but-set-variable -O3 -lgc -DGC_THREADS -DGC_PTHREADS -DPTW32_STATIC_LIB -DGC_WIN32_PTHREADS -fno-trigraphs -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -std=c11 -o test_process /home/not_synced/fuzion/build/include/shared.c /home/not_synced/fuzion/build/include/posix.c /tmp/fuzion_test_process_13769855200547668566.c' failed with exit code '1'

one error.

[maxteufel]

is this to close #559 or do you consider there to be more to that issue?