* mipsread.c (fixup_sigtramp): Also look for _sigtramp as a real

routine (for Irix-4.x).  Make many funcs static and void.
* mips-tdep.c (mips-frame-chain):  Clean up, simplify.
* (init_extra_frame_info):  Don't trash cached value of frame
pointer register.  This fixes backtracing through routines that use
alloca().  Generally clean up declarations of functions, and use
typedefs and macros to reference data structures as appropriate.
* tm-irix3.h, tm-mips.h (EXTRA_FRAME_INFO):  use proper type for
proc_desc element.

gdb/tm-mips.h

@@ -331,7 +331,7 @@ typedef struct mips_extra_func_info {
 } *mips_extra_func_info_t;
 
 #define EXTRA_FRAME_INFO \
-  char *proc_desc; /* actually, a mips_extra_func_info_t */\
+  mips_extra_func_info_t proc_desc; \
   int num_args;\
   struct frame_saved_regs *saved_regs;