spearmint: WIP: Add support for Heavy Metal: FAKK2's skelatal models

The format is also used by American McGee's Alice. Star Trek: Elite
Force 2 uses the same file extensions but it's a slight different
format -- it's not supported by this commit.

This commit draws the models but there is a few issues for full
support.

This only adds it to opengl1 renderer as it's not deemed complete,
merging into opengl2 will not be very difficult. It's missing
support for run-time level-of-detail change, trap_R_LerpTag,
dynamic bones (no CGame API), and legs rotation (I started trying
to reuse WolfET torso rotate API but it's unfinished).
There may be other issues I don't remember right now.

This is partly derived from the WolfET code for MDM+MDX (GPLv3+ with
additional terms) as it was convenient to reuse the already split
mesh and animation files. (FAKK and WolfET models are both based on
MD4 format but collapse map rendering was only in RTCW/WolfET.)

Makefile

@@ -1654,6 +1654,7 @@ Q3ROBJ = \
   $(B)/renderergl1/tr_animation.o \
   $(B)/renderergl1/tr_animation_mds.o \
   $(B)/renderergl1/tr_animation_mdm.o \
+  $(B)/renderergl1/tr_animation_skb.o \
   $(B)/renderergl1/tr_backend.o \
   $(B)/renderergl1/tr_bsp.o \
   $(B)/renderergl1/tr_cmds.o \
@@ -2157,6 +2158,7 @@ ifneq ($(SERVER_USE_RENDERER_DLOPEN),1)
     $(B)/ded/sv_ref.o \
     $(B)/ded/tr_animation_mds.o \
     $(B)/ded/tr_animation_mdm.o \
+    $(B)/ded/tr_animation_skb.o \
     $(B)/ded/tr_model.o \
     $(B)/ded/tr_model_iqm.o
 endif

code/qcommon/files.c

@@ -2748,7 +2748,7 @@ char **FS_GetFileList( const char *path, const char *extension, int *numfiles, q
 	}
 	else if (Q_stricmp(extension, "$models") == 0)
 	{
-		const char *extensions[] = { "md3", "mdr", "mdc", "mds", "mdx", "mdm", "tan", "iqm" };
+		const char *extensions[] = { "md3", "mdr", "mdc", "mds", "mdx", "mdm", "skb", "ska", "tan", "iqm" };
 		int extNamesSize = ARRAY_LEN(extensions);
 		pFiles = FS_ListFilesEx(path, extensions, extNamesSize, &nFiles, allowNonPureFilesOnDisk);
 	}

code/qcommon/qfiles.h

@@ -746,6 +746,134 @@ typedef struct {
 } mdxHeader_t;
 
 
+/*
+==============================================================================
+
+SKB file format (Heavy Metal FAKK2 Skeletal Mesh)
+
+Ritual's modified version of MD4, split into separate base (mesh) and animation files.
+
+==============================================================================
+*/
+
+#define SKB_IDENT           ( ( ' ' << 24 ) + ( 'L' << 16 ) + ( 'K' << 8 ) + 'S' )
+#define SKB_VERSION         3
+
+// Max verts for collapse map. I set it the same as RTCW/ET limits. --zturtleman
+#define SKB_MAX_VERTS 6000
+
+#define SKB_BONEFLAG_LEG        1
+
+typedef struct {
+	int boneIndex;
+	float boneWeight;
+	vec3_t offset;
+} skbWeight_t;
+
+typedef struct {
+	vec3_t normal;
+	vec2_t texCoords;
+	int numWeights;
+	skbWeight_t weights[1];     // variable sized
+} skbVertex_t;
+
+typedef struct {
+	int indexes[3];
+} skbTriangle_t;
+
+typedef struct {
+	int ident;
+
+	char name[MAX_QPATH];           // polyset name
+
+	int numTriangles;
+	int numVerts;
+	int minLod;
+
+	int ofsTriangles;
+	int ofsVerts;
+	int ofsCollapseMap;           // numVerts * int
+	int ofsEnd;                     // next surface follows
+} skbSurface_t;
+
+typedef struct {
+	int parent;
+	int flags;
+	char name[MAX_QPATH];           // name of bone
+} skbBoneInfo_t;
+
+typedef struct {
+	int ident;
+	int version;
+
+	char name[MAX_QPATH];           // model name
+
+	int numSurfaces;
+	int numBones;
+
+	int ofsBones;
+	int ofsSurfaces;
+
+	int ofsEnd;                     // end of file
+} skbHeader_t;
+
+/*
+==============================================================================
+
+SKA file format (Heavy Metal FAKK2 Skeletal Data)
+
+==============================================================================
+*/
+
+#define SKA_IDENT           ( ( 'N' << 24 ) + ( 'A' << 16 ) + ( 'K' << 8 ) + 'S' )
+#define SKA_VERSION         3
+#define SKA_MAX_BONES       256 // FIXME: Alice model has 131 bones but I haven't checked all models
+
+// NOTE: uncompressed bone/frame is only used at run-time
+typedef struct {
+	float		matrix[3][4];
+} skaBone_t;
+
+typedef struct {
+	vec3_t bounds[2];               // bounds of this frame
+	vec3_t localOrigin;
+	float radius;                   // dist from localOrigin to corner
+	vec3_t delta;                   // game movement delta
+	skaBone_t bones[1]; // [numBones]
+} skaFrame_t;
+
+typedef struct {
+	short rotate[4];
+	short offset[3];
+	short zero;
+} skaCompBone_t;
+
+typedef struct {
+	vec3_t bounds[2];       // bounds of this frame
+	float radius;           // dist from localOrigin to corner
+	vec3_t delta;           // game movement delta
+	skaCompBone_t bones[1]; // [numBones]
+} skaCompFrame_t;
+
+typedef struct {
+	int ident;
+	int version;
+
+	char name[MAX_QPATH];           // model name
+
+	int flags;
+
+	int numFrames;
+	int numBones;
+
+	float totaltime;
+	float frametime;
+	float totaldelta[3];
+
+	int ofsFrames;                  // (skaCompFrame_t + skaCompBone_t[numBones-1]) * numframes
+} skaHeader_t;
+
+
 /*
 ==============================================================================