Fix ExportDataAsCode not considering some characters for variable name

[lauchimoon]

With a fileName argument like my-image.png.h, the output inside my-image.png.h looks like this:

#define MY-IMAGE.PNG_DATA_SIZE     119076

static unsigned char MY-IMAGE.PNG_DATA[MY-IMAGE.PNG_DATA_SIZE] = ...

This commit checks if characters such as -, ., ? and ! are present in varFileName and replaces them with _, so my-image.png.h would be

#define MY_IMAGE_PNG_DATA_SIZE     119076

static unsigned char MY_IMAGE_PNG_DATA[MY_IMAGE_PNG_DATA_SIZE] = ...

[Peter0x44]

I think you have not considered enough. Filenames beginning with '+' are also not okay, as an example.
There are also multiple ExportXAsCode functions where this needs to be considered.
See #3814 as well.

[lauchimoon]

Right, I checked Ray's decision on this topic and will close the pr. Thanks!

[raysan5]

@lauchimoon I finally decided to implement this change, I merged a similar PR (#3832) but I think yours is better, please, could you resent it?

[lauchimoon]

Hi @raysan5, sure thing! If there's any other functions I should modify please lmk :)

[lauchimoon]

Will open a new PR because I've made a mess with the conflicts...