fix typos

src/gc.h

@@ -156,14 +156,14 @@ typedef struct {
 //    - pagetable0_t: the top/root level
 //    - pagetable1_t: the middle level
 //    - pagetable2_t: the bottom/leaf level
-//  Corresponding to these simlar structures is a large amount of repetetive
+//  Corresponding to these simlar structures is a large amount of repetitive
 //  code that is nearly the same but not identical. It could be made less
-//  repetetive with C macros, but only at the cost of debuggability. The specialized
+//  repetitive with C macros, but only at the cost of debuggability. The specialized
 //  structure of this representation allows us to partially unroll and optimize
 //  various conditions at each level.
 
 //  The following constants define the branching factors at each level.
-//  They constants and GC_PAGE_LG2 must therefore sum to sizeof(void*).
+//  The constants and GC_PAGE_LG2 must therefore sum to sizeof(void*).
 //  They should all be multiples of 32 (sizeof(uint32_t)) except that REGION2_PG_COUNT may also be 1.
 #ifdef _P64
 #define REGION0_PG_COUNT (1 << 16)