libsel4: Name the user context struct.

Without a name, this struct (and its typedef) comes out as an anonymous type
when imported into Isabelle. This makes it difficult to automate proofs of
functions that use this type.

See also JIRA VER-434

libsel4/arch_include/arm/sel4/arch/types.h

@@ -37,7 +37,7 @@ typedef seL4_CPtr seL4_ARM_PageDirectory;
 typedef seL4_CPtr seL4_ARM_ASIDControl;
 typedef seL4_CPtr seL4_ARM_ASIDPool;
 
-typedef struct {
+typedef struct seL4_UserContext_ {
     /* frame registers */
     seL4_Word pc, sp, cpsr, r0, r1, r8, r9, r10, r11, r12;
     /* other integer registers */

libsel4/arch_include/ia32/sel4/arch/types.h

@@ -37,7 +37,7 @@ typedef seL4_CPtr seL4_IA32_IOPageTable;
 
 /* User context as used by seL4_TCB_ReadRegisters / seL4_TCB_WriteRegisters */
 
-typedef struct {
+typedef struct seL4_UserContext_ {
     /* frameRegisters */
     seL4_Word eip, esp, eflags, eax, ebx, ecx, edx, esi, edi, ebp;
     /* gpRegisters */