kernel/x86_64: add compatibility source files to the build.

* add x86 versions of fnsave frstor.
* add missing declaration for elf32_resolve_symbol().

How-to build a x86_64/x86 bootstrap build:
mkdir generated_bootstrap; cd generated_bootstrap
../configure --bootstrap /dir/to/haikuporter/haikuporter /dir/to/haikuports.cross \
  /dir/to/haikuports --build-cross-tools x86_64 /dir/to/buildtools --build-cross-tools x86 -j8 --use-gcc-pipe
jam -q -sHAIKU_PORTER_EXTRA_OPTIONS="-j8 --sourceforge-mirror=freefr --no-source-packages" @bootstrap-raw

Change-Id: I6eae3653c42a53683ae307107fae595c4b8ebcfb

headers/private/kernel/arch/x86/arch_cpu.h

@@ -579,9 +579,6 @@ void x86_write_msr(uint32 registerNumber, uint64 value);
 void x86_context_switch(struct arch_thread* oldState,
 	struct arch_thread* newState);
 
-void x86_fnsave(void* fpuState);
-void x86_frstor(const void* fpuState);
-
 void x86_fxsave(void* fpuState);
 void x86_fxrstor(const void* fpuState);
 
@@ -592,6 +589,14 @@ void x86_fxsave_swap(void* oldFpuState, const void* newFpuState);
 #endif
 
 
+#if !defined(__x86_64__) || defined(_COMPAT_MODE)
+
+void x86_fnsave(void* fpuState);
+void x86_frstor(const void* fpuState);
+
+#endif // !defined(__x86_64__) || defined(_COMPAT_MODE)
+
+
 static inline void
 arch_cpu_idle(void)
 {

headers/private/kernel/elf_priv.h

@@ -82,6 +82,11 @@ extern "C" {
 extern status_t elf_resolve_symbol(struct elf_image_info* image,
 	elf_sym* symbol, struct elf_image_info* sharedImage,
 	elf_addr* _symbolAddress);
+#ifdef _COMPAT_MODE
+extern status_t elf32_resolve_symbol(struct elf_image_info* image,
+	elf_sym* symbol, struct elf_image_info* sharedImage,
+	elf_addr* _symbolAddress);
+#endif
 
 #ifdef __cplusplus
 }