Compiler: Add #pragma deprecated.

This is based on SM, including patch to support macros/constants (https://hg.alliedmods.net/sourcemod-central/rev/ef8dd1cddc35).
Updated also some pawn includes to use this new pragma.

plugins/include/amxmodx.inc

@@ -2535,6 +2535,7 @@ native plugin_flags(hdr=0, plid=-1);
  *
  * @noreturn
  */
+#pragma deprecated Module dependency is now automatically handled by the compiler. This forward is no longer called.
 forward plugin_modules();
 
 /**
@@ -2545,6 +2546,7 @@ forward plugin_modules();
  *
  * @noreturn
  */
+#pragma deprecated Module dependency is now automatically handled by the compiler. This native has no effect.
 native require_module(const module[]);
 
 /**
@@ -2556,6 +2558,7 @@ native require_module(const module[]);
  *
  * @return  1 if the server is 64 bit, 0 otherwise
  */
+#pragma deprecated AMXX is not shipping 64bits builds anymore. This native is basically guaranteed to return 0.
 native is_amd64_server();
 
 /**

plugins/include/geoip.inc

@@ -62,7 +62,7 @@ native bool:geoip_code3_ex(const ip[], result[4]);
  *
  * @return          1 on a successful lookup, 0 otherwise.
  */
-//#pragma deprecated Use geoip_code2_ex() instead.
+#pragma deprecated Use geoip_code2_ex() instead.
 native geoip_code2(const ip[], ccode[3]);
 
 /**
@@ -76,7 +76,7 @@ native geoip_code2(const ip[], ccode[3]);
  *
  * @return          1 on a successful lookup, 0 otherwise.
  */
-//#pragma deprecated Use geoip_code3() instead.
+#pragma deprecated Use geoip_code3() instead.
 native geoip_code3(const ip[], result[4]);
 
 /**

plugins/include/ns.inc

@@ -543,6 +543,7 @@ forward client_spawn(id);
  * @param Damage		The amount of damage being done.
  * @param DamageType	The damage type being done (bitmask).
  */
+#pragma deprecated It is suggested to use hamsandwich for this action instead.
 native ns_takedamage(IDVictim, IDInflictor, IDAttacker, Float:Damage, DamageType);
 
 /**

plugins/include/string.inc

@@ -711,7 +711,7 @@ native strncmp(const string1[], const string2[], num, bool:ignorecase=false);
  * Backwards compatibility stock - use argbreak or argparse.
  * @deprecated			this function does not work properly.
  */
-//#pragma deprecated Use argbreak() instead
+#pragma deprecated Use argbreak() instead
 stock strbreak(const text[], Left[], leftLen, Right[], rightLen)
 {
 	return argbreak(text, Left, leftLen, Right, rightLen);