[rcore] Fix GetFileNameWithoutExt()

[oblerion]

puts( GetFileNameWithoutExt("dir/file.name.zip") ); 
// out : "file"

[with fix]

puts( GetFileNameWithoutExt("dir/file.name.zip") );
// out : "file.name"

Use reverse search '.' for remove extension.

[Peter0x44]

Not entirely related to the PR but this is one of the (many) operations that becomes so much easier if you stop using null-terminated strings

#define s8(s) (s8) { (unsigned char*) s, (ptrdiff_t) sizeof(s)-1 }

typedef struct
{
	unsigned char* str;
	ptrdiff_t len;
} s8;

s8 GetExtensionlessFilename(s8 fileName)
{
	s8 ret = fileName;
	for (ptrdiff_t i = ret.len-1; i >= 0; --i)
	{
		--ret.len;
		if (ret.str[i] == '.') return ret;
	}
	return fileName;
}

You can eliminate the need to copy the string (and therefore skip the hardcoded size static buffer), and also the O(n) useless strlen call.

It's only an issue if you need to pass the string later on to something that expects null-terminated, which is unfortunately common.

(not suggesting or implying raylib should change its string convention - just wanted to "spread awareness" I guess)

[oblerion]

It's fix thank for help Peter0x44 and raysan5

[raysan5]

@oblerion thank you very much for the review!