Fix No spread on the hl2_complete server build

The server RandomSeed GOT slot was hardcoded to 0xce1348, measured on the
older bin/server.so. The anniversary branch loads hl2_complete/bin/server.so,
whose R_386_JMP_SLOT for RandomSeed is 0xce5348, so the patch hit unrelated
writable data and no spread silently did nothing.

- Read the relocation from the loaded module's ELF (module_jump_slot) instead
  of hardcoding, with the two known offsets as fallback.
- Override whenever the RandomSeed caller's `this` is the local server player
  (CBaseEntity::FireBullets) instead of matching a hardcoded return-address
  range that also moved between builds.
- m_takedamage is a char (FIELD_CHARACTER) in the 2013 SDK; resolve it as such
  and read a byte, so the IMMUNE damage tag actually works.

1 files changed, 8 insertions, 3 deletions

diff --git a/src/server.cpp b/src/server.cpp
index e9fd921..f71b441 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -142,7 +142,11 @@ bool resolve_server_netvars() {
   g_srv_spawnflags = datamap_offset("m_spawnflags", FIELD_INTEGER, 0x4);
   g_srv_hacked = datamap_offset("m_bHackedByAlyx", FIELD_BOOLEAN);
   g_srv_npcstate = datamap_offset("m_NPCState", FIELD_INTEGER);
-  g_srv_takedamage = datamap_offset("m_takedamage", FIELD_INTEGER);
+  // CBaseEntity::m_takedamage is a char in the 2013 SDK
+  // (CNetworkVarForDerived(char, m_takedamage)); older builds used int.
+  g_srv_takedamage = datamap_offset("m_takedamage", FIELD_CHARACTER);
+  if (g_srv_takedamage < 0)
+    g_srv_takedamage = datamap_offset("m_takedamage", FIELD_INTEGER);
   g_srv_ready = g_srv_health > 0;
   if (g_srv_ready) {
     logf("server datamap (%s): health=%d maxhealth=%d lifeste=%d "
@@ -272,7 +276,8 @@ int server_npc_state(int idx) {
 }
 
 // TAKEDAMAGE: 0 = DAMAGE_NO, 1 = DAMAGE_EVENTS_ONLY, 2 = DAMAGE_YES,
-// 3 = DAMAGE_AIM. 0/1 cannot be damaged at all.
+// 3 = DAMAGE_AIM. 0/1 cannot be damaged at all. The field is a char, so read
+// a byte even if the older int layout was resolved.
 int server_npc_takedamage(int idx) {
   if (!g_srv_ready || g_srv_takedamage < 0)
     return -1;
@@ -280,7 +285,7 @@ int server_npc_takedamage(int idx) {
   server_entity_health(idx, nullptr, nullptr, &base);
   if (!base)
     return -1;
-  return *(int *)((uintptr_t)base + g_srv_takedamage);
+  return (int)*(unsigned char *)((uintptr_t)base + g_srv_takedamage);
 }
 
 bool server_npc_has_follow_target(int idx) {