Fix usage of bx::findIdentifierMatch for gl_FragDepth (#2533)
Fix usage of bx::findIdentifierMatch for gl_FragDepth (#2533)

When trying to find all the instances of gl_FragDepth
and replace them with bgfx_FragDepth it only finds
the first instance.
LWJGL-CI/bgfx,jdryg/bgfx,emoon/bgfx,LWJGL-CI/bgfx,bkaradzic/bgfx,LWJGL-CI/bgfx,jdryg/bgfx,bkaradzic/bgfx,LWJGL-CI/bgfx,emoon/bgfx,bkaradzic/bgfx,jdryg/bgfx,bkaradzic/bgfx,emoon/bgfx,jdryg/bgfx