Make ConVar cache case insensitive, fixes #1166

[sm9cc]

Test code:

public void OnPluginStart() {
	ConVar SV_CHEATS = FindConVar("SV_CHEATS");
	ConVar sv_cheats = FindConVar("sv_cheats");
	ConVar sV_cHeAtS = FindConVar("sV_cHeAtS");
	
	LogMessage("'SV_CHEATS' = %i, 'sv_cheats' = %i, 'sV_cHeAtS' = %i", SV_CHEATS, sv_cheats, sV_cHeAtS);
}

Output:

L 02/10/2020 - 09:04:54: [ConVarLeakTest.smx] 'SV_CHEATS' = 4718664, 'sv_cheats' = 4718664, 'sV_cHeAtS' = 4718664

[nosoop]

Confirmed working on TF2 with a similar case (convar ai_LOS_mode being not all lowercase):

// Test
ConVar t = CreateConVar("TTTTT", "0.1");
PrintToServer("T0 %d %d", t, FindConVar("TTTTT")); // SAME
PrintToServer("T1 %d", FindConVar("tTTTT")); // ALWAYS DIFFERENT
PrintToServer("T2 %d", FindConVar("TtTTT")); // ALWAYS DIFFERENT
PrintToServer("T3 %d", FindConVar("TTtTT")); // ALWAYS DIFFERENT

// Real cvar registered as: Smoker_escape_range
PrintToServer("A %d", FindConVar("ai_los_mode")); // ALWAYS DIFFERENT
PrintToServer("B %d", FindConVar("ai_los_mode")); // ALWAYS DIFFERENT
PrintToServer("C %d", FindConVar("ai_los_mode")); // ALWAYS DIFFERENT
PrintToServer("D %d", FindConVar("ai_LOS_mode")); // ALWAYS SAME
PrintToServer("E %d", FindConVar("ai_LOS_mode")); // ALWAYS SAME
PrintToServer("F %d", FindConVar("ai_LOS_mode")); // ALWAYS SAME

Results on SM without PR:

T0 878053395 878053395
T1 878118929
T2 878184463
T3 878249997
A 878315531
B 878381065
C 878446599
D 878512085
E 878512085
F 878512085

Results with PR:

T0 11141280 11141280
T1 11141280
T2 11141280
T3 11141280
A 11206819
B 11206819
C 11206819
D 11206819
E 11206819
F 11206819

[sm9cc]

Confirmed working in L4D2 with original test code (After PR):

 // Test
ConVar t = CreateConVar("TTTTT", "0.1");
PrintToServer("T0 %d %d", t, FindConVar("TTTTT")); // SAME
PrintToServer("T1 %d", FindConVar("tTTTT")); // ALWAYS DIFFERENT
PrintToServer("T2 %d", FindConVar("TtTTT")); // ALWAYS DIFFERENT
PrintToServer("T3 %d", FindConVar("TTtTT")); // ALWAYS DIFFERENT

// Real cvar registered as: Smoker_escape_range
PrintToServer("A %d", FindConVar("smoker_escape_range")); // ALWAYS DIFFERENT
PrintToServer("B %d", FindConVar("smoker_escape_range")); // ALWAYS DIFFERENT
PrintToServer("C %d", FindConVar("smoker_escape_range")); // ALWAYS DIFFERENT
PrintToServer("D %d", FindConVar("Smoker_escape_range")); // ALWAYS SAME
PrintToServer("E %d", FindConVar("Smoker_escape_range")); // ALWAYS SAME
PrintToServer("F %d", FindConVar("Smoker_escape_range")); // ALWAYS SAME

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[SM] Plugin ConVarLeakTest.smx reloaded successfully.
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[SM] Plugin ConVarLeakTest.smx reloaded successfully.
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[SM] Plugin ConVarLeakTest.smx reloaded successfully.
] sm plugins reload ConVarLeakTest
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[SM] Plugin ConVarLeakTest.smx reloaded successfully.

[Headline]

Thank you!