highgui: use forward slash for gl.h include
authorTony Theodore <tonyt@logyst.com>
Sun, 5 Feb 2017 17:15:10 +0000 (04:15 +1100)
committerTony Theodore <tonyt@logyst.com>
Sun, 5 Feb 2017 17:15:10 +0000 (04:15 +1100)
commit678e114e5fc3fddc23f3ec1619a479895d0707ca
tree8c6e94abcb96fa94112d799d2039c4831d1703b5
parenta2fed4c790cafea5a00628c844ccd0a34c6479a6
highgui: use forward slash for gl.h include

The backslash causes build failure when cross-compiling with mingw-w64
modules/highgui/src/window_w32.cpp