Uhm, thats strange because it actually should include the window.h header file which includes the realloc function prototype. Three questions:
Can you compile the examples like arrays.c?
What Gamestudio version do you use?
Does the LFBase.h header look like this (the first three actual lines)?
//#define LF_TARGET_OSX
#define LF_TARGET_WIN32
#define LF_TARGET_LITEC // Needs to be combined with LF_TARGET_WIN32!