stb_image: Fix -Wdouble-promotion warning

Upstream PR 1902 by Björn Wahlstrand at https://github.com/nothings/stb

src/video/stb_image.h

@@ -101,7 +101,7 @@ RECENT REVISION HISTORY:
     Marc LeBlanc            David Woo          Guillaume George     Martins Mozeiko
     Christpher Lloyd        Jerry Jansson      Joseph Thomson       Blazej Dariusz Roszkowski
     Phil Jordan             Henner Zeller      Dave Moore           Roy Eltham
-    Hayaki Saito            Nathan Reed        Won Chun
+    Hayaki Saito            Nathan Reed        Won Chun             Björn Wahlstrand
     Luke Graham             Johan Duparc       Nick Verigakis       the Horde3D community
     Thomas Ruf              Ronny Chevalier                         github:rlyeh
     Janez Zemva             John Bartholomew   Michal Cichon        github:romigrou
@@ -2586,7 +2586,7 @@ stbi_inline static stbi_uc stbi__clamp(int x)
    return (stbi_uc) x;
 }
 
-#define stbi__f2f(x)  ((int) (((x) * 4096 + 0.5)))
+#define stbi__f2f(x)  ((int) (((x) * 4096 + 0.5f)))
 #define stbi__fsh(x)  ((x) * 4096)
 
 // derived from jidctint -- DCT_ISLOW