Fix the debug keyboard failing to type.

A bug introduced in 332dd43 caused the keyboard to locally modify the source strings, and then discard the changes without writing them back to the original string.
This change drops the use of snprintf to perform the changes entirely, opting instead for twiddling the characters in-place.
This required changing the bounds check to ensure there remains room for the null-terminator, and a call to strlen was refactored to be stored for the local scope.

Author: SilverNexus2

src/debug/pspdebugkb.c

@@ -249,13 +249,17 @@ void pspDebugKbInit(char* str) {
 	  pspDebugKbShift(&shifted);
 	  pspDebugKbDrawKey(row, col, 1);
 	  break;
-	case 1: // Space
-	  if (strlen(str) < PSP_DEBUG_KB_MAXLEN) {
-	    char out[PSP_DEBUG_KB_MAXLEN + 2];
-	    snprintf(out, sizeof(out), "%s ", str);
-	    pspDebugKbDrawString(out);
+	// Using the curly braces so we have an anonymous code block so we can declare a stack variable
+	case 1: { // Space
+	  size_t len = strlen(str);
+	  if (len < PSP_DEBUG_KB_MAXLEN-1) {
+	    // Add the character to the still-in-bounds string
+	    str[len] = ' ';
+	    str[len+1] = '\0';
+	    pspDebugKbDrawString(str);
 	  }
 	  break;
+	}
 	case 2: // Back
 	  if (strlen(str) > 0) {
 	    str[strlen(str)-1] = '\0';
@@ -272,10 +276,14 @@ void pspDebugKbInit(char* str) {
 	  return;
 	};
       } else {
-	if (strlen(str) < PSP_DEBUG_KB_MAXLEN) {
-	  char out[PSP_DEBUG_KB_MAXLEN + 2];
-	  snprintf(out, sizeof(out), "%s%c", str, charTable[row][col]);
-	  pspDebugKbDrawString(out);
+	size_t len = strlen(str);
+	// Leave room for null terminator
+	if (len < PSP_DEBUG_KB_MAXLEN-1) {
+	  // Add the character to the still-in-bounds string
+	  str[len] = charTable[row][col];
+	  str[len+1] = '\0';
+	  // Display the string
+	  pspDebugKbDrawString(str);
 	}
       }
     }