changelog: fix typo CSIGN/CUNSG

(cherry picked from commit 7f201c9)

# Conflicts:
#	changelog.txt

Author: jayrm

changelog.txt

@@ -14,7 +14,7 @@ Version 1.07.2
 [fixed]
 - sf.net #921: gfxlib: horizontal line drawing on 8-bit image was using wrong bpp
 - github #258: on windows directx and gdi drivers, only show window after intialization is complete (adeyblue)
-- sf.net #925: CSIGN/CUSGN preserve size when converting pointers on 64-bit and implict conversion of STEP value in FOR...NEXT statement
+- sf.net #925: CSIGN/CUNSG preserve size when converting pointers on 64-bit and implict conversion of STEP value in FOR...NEXT statement
 
 
 Version 1.07.1