Change GuiStyleProp propertyValue from int to unsigned int

[tyqualters]

VERSION raylib 5.0 / raygui 4.0

raygui.h line 450

typedef struct GuiStyleProp {
    unsigned short controlId;   // Control identifier
    unsigned short propertyId;  // Property identifier
    int propertyValue;          // Property value
} GuiStyleProp;

Requesting change int propertyValue; to unsigned int propertyValue;

typedef struct GuiStyleProp {
    unsigned short controlId;   // Control identifier
    unsigned short propertyId;  // Property identifier
    unsigned int propertyValue;          // Property value
} GuiStyleProp;

Reason being that there is a possible narrowing conversion to MAXINT, and C++ (unlike C) will throw a lot of errors when trying to use any of the default styles (e.g. /styles/cyber/stylecyber.h) because of this narrowing conversion. This change fixes that issue and allows C++ to build.

[raysan5]

@tyqualters I'm afraid it's not possible to change this type because some properties could have negative values, for example TEXT_SPACING.