Fix spelling bugs and compiler warnings

Index: cpu-exec.c
===================================================================
@@ -882,6 +882,8 @@
        do it (XXX: use sigsetjmp) */
     sigprocmask(SIG_SETMASK, old_set, NULL);
     cpu_loop_exit();
+    /* never comes here */
+    return 1;
 }
 #elif defined(TARGET_SPARC)
 static inline int handle_cpu_signal(unsigned long pc, unsigned long address,

@@ -918,6 +920,8 @@
        do it (XXX: use sigsetjmp) */
     sigprocmask(SIG_SETMASK, old_set, NULL);
     cpu_loop_exit();
+    /* never comes here */
+    return 1;
 }
 #elif defined (TARGET_PPC)
 static inline int handle_cpu_signal(unsigned long pc, unsigned long address,

Index: hw/e1000_hw.h
===================================================================
@@ -734,7 +734,7 @@
     uint16_t special;
 };
 
-/* Receive Decriptor bit definitions */
+/* Receive Descriptor bit definitions */
 #define E1000_RXD_STAT_DD       0x01    /* Descriptor Done */
 #define E1000_RXD_STAT_EOP      0x02    /* End of Packet */
 #define E1000_RXD_STAT_IXSM     0x04    /* Ignore checksum */

Index: hw/stellaris.c
===================================================================
@@ -1,5 +1,5 @@
 /*
- * Luminary Micro Stellaris preipherals
+ * Luminary Micro Stellaris peripherals
  *
  * Copyright (c) 2006 CodeSourcery.
  * Written by Paul Brook

Index: target-arm/neon_helper.c
===================================================================
@@ -726,7 +726,7 @@
 NEON_VOP(mul_u16, neon_u16, 2)
 #undef NEON_FN
 
-/* Polynomial multiplication is like integer multiplcation except the
+/* Polynomial multiplication is like integer multiplication except the
    partial products are XORed, not added.  */
 uint32_t HELPER(neon_mul_p8)(uint32_t op1, uint32_t op2)
 {

Index: target-arm/helper.c
===================================================================
@@ -1908,7 +1908,7 @@
 
 /* Signed saturating arithmetic.  */
 
-/* Perform 16-bit signed satruating addition.  */
+/* Perform 16-bit signed saturating addition.  */
 static inline uint16_t add16_sat(uint16_t a, uint16_t b)
 {
     uint16_t res;

@@ -1923,7 +1923,7 @@
     return res;
 }
 
-/* Perform 8-bit signed satruating addition.  */
+/* Perform 8-bit signed saturating addition.  */
 static inline uint8_t add8_sat(uint8_t a, uint8_t b)
 {
     uint8_t res;

@@ -1938,7 +1938,7 @@
     return res;
 }
 
-/* Perform 16-bit signed satruating subtraction.  */
+/* Perform 16-bit signed saturating subtraction.  */
 static inline uint16_t sub16_sat(uint16_t a, uint16_t b)
 {
     uint16_t res;

@@ -1953,7 +1953,7 @@
     return res;
 }
 
-/* Perform 8-bit signed satruating subtraction.  */
+/* Perform 8-bit signed saturating subtraction.  */
 static inline uint8_t sub8_sat(uint8_t a, uint8_t b)
 {
     uint8_t res;