Riccardom warnings fixes patches:

- cflash.cpp: this was straightforward, i've moved p declaration only
because there it's easier to follow where it is used.
- GPU.cpp: that functions is very long and has an horrible formatting,
please review.
- MMU.cpp: return in case of default inside a switch is used often inside
the code so i've done the same.

desmume/src/GPU.cpp

@@ -2140,10 +2140,15 @@ else
 				case 2:
 					capx = 256;
 					capy = 128;
+					break;
 				case 3:
 					capx = 256;
 					capy = 192;
 					break;
+				default:
+					capx = 0;
+					capy = 0;
+					break;
 			}
 			
 			if(l < capy)	/* check if our line is in cature area */

desmume/src/MMU.cpp

@@ -3095,6 +3095,8 @@ void FASTCALL MMU_doDMA(u32 proc, u32 num)
 			case 1 :  dstinc = -sz; break;
 			case 2 :  dstinc =   0; break;
 			case 3 :  dstinc =  sz; break; //reload
+			default:
+				return;
 		}
 		switch((u >> 2)&0x3) {
 			case 0 :  srcinc =  sz; break;
@@ -3102,6 +3104,8 @@ void FASTCALL MMU_doDMA(u32 proc, u32 num)
 			case 2 :  srcinc =   0; break;
 			case 3 :  // reserved
 				return;
+			default:
+				return;
 		}
 		if ((MMU.DMACrt[proc][num]>>26)&1)
 			for(; i < taille; ++i)

desmume/src/cflash.cpp

@@ -152,7 +152,6 @@ static const int lfnPos[13] = {1,3,5,7,9,14,16,18,20,22,24,28,30};
 static void add_file(char *fname, FsEntry * entry, int fileLevel) {
 	int i,j,k,n;
         u8 chk;
-	char *p;
 
 	if (numFiles < MAXFILES-1) {
 		if (strcmp(fname,"..") != 0) {
@@ -175,6 +174,8 @@ static void add_file(char *fname, FsEntry * entry, int fileLevel) {
 
 			// See if LFN entries need to be added
 			if (strlen(entry->cAlternateFileName)>0) {
+				char *p = NULL;
+
 				chk = lfn_checksum();
 				k = (strlen(entry->cFileName)/13) + (((strlen(entry->cFileName)%13)!=0)?1:0);
 				numFiles += k;
@@ -201,7 +202,8 @@ static void add_file(char *fname, FsEntry * entry, int fileLevel) {
 					*(p + lfnPos[j]) = entry->cFileName[i];
 					*(p + lfnPos[j]+1) = 0;
 				}
-				p[0] |= 0x40;	// END
+				if (p != NULL)
+					p[0] |= 0x40;	// END
 				for (i=strlen(fname)-1; i>=0; i--)
 					if (fname[i]=='.') break;
 				if ((i==0)&&(strcmp(fname,".")==0)) i = 1;