renderer: fix vertex lighting with terrain blending and with non-style lightmap with tcGen lightmap

[illwieckz]

I guess I've set that value after some trial and error to workaround what I didn't knew was a bug, but I fixed that bug later.

In the current state of the renderer, I don't see bugs popping when removing that part, and this is needed to fix terrain blending.

I also added a commit fixing some bad spacing that was mistakenly merged.

[illwieckz]

In thunder map, terrain blending was already working with vertex lighting, but the two stages are opaque:

textures/thunder_custom/ter_rocksand_xy
{
	qer_editorImage textures/thunder_custom_src/ter_rocksand_p

	q3map_nonplanar
	q3map_shadeAngle 90
	q3map_tcGen ivector ( 256 0 0 ) ( 0 256 0 )
	q3map_alphaMod dotproduct2 ( 0 0 .75 )

	{
		diffuseMap textures/shared_pk02_src/rock01_d
		normalMap textures/shared_pk02_src/rock01_n
		specularMap textures/shared_pk02_src/rock01_s
		rgbGen identity
	}
	{
		diffuseMap textures/shared_pk02_src/sand01_d
		normalMap textures/shared_pk02_src/sand01_n
		specularMap textures/shared_pk02_src/sand01_s
		blendFunc blend
		alphaGen vertex
	}
}

In station15, terrain blending was broken with vertex lighting, as one of the stage is not opaque and the code was resetting the alpha channel:

textures/station15_custom/ter_mudmoss1
{
	qer_editorImage textures/station15_custom_src/ter_mudmoss1_p

	q3map_nonplanar
	q3map_shadeangle 120
	q3map_tcGen ivector ( 256 0 0 ) ( 0 256 0 )
	q3map_alphaMod dotproduct2 ( 0 0 .75 )

	{
		diffuseMap textures/station15_custom_src/ter_moss1_d
		rgbGen identity
	}
	{
		diffuseMap textures/station15_custom_src/ter_mud1_d
		blendFunc GL_SRC_ALPHA GL_ONE_MINUS_SRC_ALPHA
		alphaFunc GE128
		rgbGen identity
		alphaGen vertex
	}
}

Here is how it now works:

I don't see anymore any problem with other maps, example here with rusty (before/after) that was the map I was used when testing vertex lighting and then when I wrote that original code:

I also tested other maps like wolf:et oasis wich is known to do complex mixed lightmap/vertex ligthing and I see no regression when enabling vertex lighting or light mapping.

Scenes used to debug:

map	viewpos
thunder	3906 473 142 47 13
station15	532 -1189 21 -180 34
rusty	-1134 -2261 111 31 8

[illwieckz]

I added a commit to add a debug cvar named r_showVertexColors to render the vertex colors used for vertex lighting:

[illwieckz]

I added a commit making a difference between a light style map and a light map with useless “tcGen lightmap”.

This fixes #1027:

• Fullbright pipe in cruz map with vertex lighting #1027

I verified this don't break light styled maps like gloom2 and pulse.

Before, after:

[slipher]

LGTM