Another round of GCC fixes (#3115)

* Fix remaining <string> -> <cstring> for GCC compilation (#3114 follow-up)

MWerks' <string> header transitively includes C string functions
(memcpy, strlen, strcmp, etc.), but GCC/Clang's <string> is the C++
std::string header. These files all use C string functions and should
include <cstring> instead.

* Use std::isnan instead of isnan for GCC compilation

GCC's <cmath> places isnan in the std namespace. Using the unqualified
isnan fails to compile with GCC/Clang.

* Fix cCcD_Src types: s32 -> u32 for bitmask fields

cCcD_SrcObjCommonBase::mSPrm, cCcD_SrcObjTg::mType, and
cCcD_SrcObjAt::mType are used as bitmasks (SetType/SetSPrm take u32,
MskType/MskSPrm use u32, values like 0xFFFFFFFF are common in
aggregate inits). Change from s32 to u32 to match usage.

Also fix AT_TYPE_WOLF_ATTACK/AT_TYPE_UNK to use unsigned literals,
and remove now-unnecessary (s32) casts on hex literals in collision
source data.

* Mark dummy() functions as static to avoid multiple definition errors

These decomp artifact functions have the same name and signature across
TUs, causing linker errors when building as a single binary.

src/d/actor/d_a_e_dk.cpp

@@ -46,7 +46,7 @@ enum E_DK_RES_FILE_ID {
 namespace {
 static dCcD_SrcSph cc_dk_src = {
     { // mObjInf
-        { 0x0, { { 0, 0, { 0 } }, { (s32)0xd8fbbddf, { 3 } }, { { 0x75 } } } }, // mObj
+        { 0x0, { { 0, 0, { 0 } }, { 0xd8fbbddf, { 3 } }, { { 0x75 } } } }, // mObj
         { 0x09, 0, 0, 0, { 0 } }, // mGObjAt
         { 0x00, 0x00, 0x00, 0x00, { 5 } }, // mGObjTg
         { { 0 } }, // mGObjCo