Fix MeasureTextEx() height calculation

[marrony]

For multiline strings MeasureTextEx() is returning a much higher value than the actual text height.

Pretty much like DrawTextEx() this patch just increment textLineSpacing in the height when it sees \n and don't apply scaleFactor at the end.

Small program to simulate the issue:

#include <stdlib.h>
#include "raylib.h"

int main(void) {
  InitWindow(200, 100, "MeasureTextEx");

  Font font = GetFontDefault();

  while (!WindowShouldClose()) {
    BeginDrawing();
    ClearBackground(WHITE);

    const char *text = "Some\nMultiline\nText";
    float fontSize = 20;
    float spacing = 5;

    SetTextLineSpacing(fontSize + 4);
    DrawTextEx(font, text, (Vector2){10, 10}, fontSize, spacing, BLACK);

    // draw red box around text
    Vector2 m = MeasureTextEx(font, text, fontSize, spacing);
    DrawRectangleLinesEx((Rectangle){10, 10, m.x, m.y}, 1, RED);

    EndDrawing();
  }

  CloseWindow();
  return 0;
}

Without the fix

With the fix

[raysan5]

@marrony thanks for the review! It should fix issue #3745