String leak (userAgent)

[hrydgard]

At least on Windows, naett seems to leak some strings set by stringSetter.

Report after running (it just leaks the user agent string):

C:\dev\ppsspp\ext\naett\naett.c(154) : {4247868} normal block at 0x0000021496CEE120, 31 bytes long.
 Data: <PPSSPP/v1.16.5-1> 50 50 53 53 50 50 2F 76 31 2E 31 36 2E 35 2D 31 
C:\dev\ppsspp\ext\naett\naett.c(154) : {4243564} normal block at 0x0000021496CE9E00, 31 bytes long.
 Data: <PPSSPP/v1.16.5-1> 50 50 53 53 50 50 2F 76 31 2E 31 36 2E 35 2D 31 
C:\dev\ppsspp\ext\naett\naett.c(154) : {4241788} normal block at 0x0000021496CEE1E0, 31 bytes long.
 Data: <PPSSPP/v1.16.5-1> 50 50 53 53 50 50 2F 76 31 2E 31 36 2E 35 2D 31 
C:\dev\ppsspp\ext\naett\naett.c(154) : {4067325} normal block at 0x0000021496CE8D80, 31 bytes long.
 Data: <PPSSPP/v1.16.5-1> 50 50 53 53 50 50 2F 76 31 2E 31 36 2E 35 2D 31 

naett.c(154) is simply char* stringCopy = strdup(param->string);.