[rtext] incorrect handling of decimal point in TextToFloat

[ListeriaM]

• I tested it on latest raylib version from master branch
• I checked there is no similar issue already reported
• I checked the documentation on the wiki
• My code has no errors or misuse of raylib

Issue description

The function can't return a negative value if there is a decimal point.

Code Example

#include <raylib.h>

static void parse(const char *text)
{
	TraceLog(LOG_INFO, "TextToFloat(\"%s\") = %g", text, TextToFloat(text));
}

int main(void)
{
	parse("-1");
	parse("-1.");
	parse("-1.5");
}

output:

INFO: TextToFloat("-1") = -1
INFO: TextToFloat("-1.") = 1
INFO: TextToFloat("-1.5") = 1.5