Revert "Fix gcc compile error: redundant redeclaration of ‘environ’ [-Werror=redundant-decls]"
Breaks the build on FreeBSD which doens't have an environ declaration.
The CMake check_symbol_exists call sets HAVE_DECL_ENVIRON
to an empty
variable (which means if(DEFINED) suceeds). This normalization should not
be necessary as it will be handled correctly by #cmakedefine01
. If not,
all the other HAVE_* defines would also be wrong.
This reverts commit e8b34b41.