kernel: delete syscall, bump required fox32rom API version to 2

fox32os.def

@@ -48,6 +48,7 @@ read:                      jmp [0x00000D1C]
 write:                     jmp [0x00000D20]
 get_size:                  jmp [0x00000D24]
 create:                    jmp [0x00000D28]
+delete:                    jmp [0x00000D2C]
 
 ; widget jump table
 draw_widgets_to_window:    jmp [0x00000E10]

kernel/main.asm

@@ -10,7 +10,7 @@ const FOX32OS_VERSION_PATCH: 0
 
 const FOX32OS_API_VERSION: 1
 
-const REQUIRED_FOX32ROM_API_VERSION: 1
+const REQUIRED_FOX32ROM_API_VERSION: 2
 
 const SYSTEM_STACK:     0x01FFF800
 const BACKGROUND_COLOR: 0xFF674764
@@ -73,6 +73,7 @@ jump_table:
     data.32 write
     data.32 get_size
     data.32 create
+    data.32 delete
 
     ; widget jump table
     org.pad 0x00000610

kernel/vfs/vfs.asm

@@ -102,6 +102,7 @@ open_stream:
     ret
 
 ; create a file on a RYFS-formatted disk, or open a named stream
+; if target file already exists, it will be deleted and then re-created as a blank file
 ; inputs:
 ; r0: pointer to file name string (8.3 format if file, for example "testfile.txt" or "test.txt")
 ; r1: disk ID (ignored if stream)
@@ -118,6 +119,16 @@ create:
     ifz ret
     jmp ryfs_create
 
+; delete a file on a RYFS-formatted disk
+; inputs:
+; r0: file struct: pointer to a filled file struct
+; outputs:
+; none
+delete:
+    cmp r0, 0
+    ifz ret
+    jmp ryfs_delete
+
 ; seek specified file to the specified offset
 ; inputs:
 ; r0: byte offset