[3038] Remove all traces of MANGOS_DLL_DECL, which is a useless define these days. See cmangos/issues#402 for details.

Signed-off-by: xfurry <xfurry@scriptdev2.com>
[3039] Fix a GCC compiler warning. The type of the second argument of memset is int, not float.

Signed-off-by: xfurry <xfurry@scriptdev2.com>
[3040] Fix code using 'false' as return value where type 'const SpellEntry*' is expected.

Signed-off-by: xfurry <xfurry@scriptdev2.com>
[3041] Fix a bunch of GCC compiler warnings about missing field initializers [-Wmissing-field-initializers].

Close #114

Signed-off-by: xfurry <xfurry@scriptdev2.com>