chore: fix some typos in comments (#3096)

Signed-off-by: goodactive <goodactive@qq.com>

src/decNumber/decBasic.c

@@ -756,7 +756,7 @@ static void decFiniteMultiply(bcdnum *num, uByte *bcdacc,
   #endif
 
   /* Effect the multiplication */
-  // The multiplcation proceeds using MFC's lazy-carry resolution
+  // The multiplication proceeds using MFC's lazy-carry resolution
   // algorithm from decNumber.  First, the multiplication is
   // effected, allowing accumulation of the partial products (which
   // are in base-billion at each column position) into 64 bits

src/decNumber/decNumber.c

@@ -2168,7 +2168,7 @@ decNumber * decNumberPower(decNumber *res, const decNumber *lhs,
       // if a negative power the constant 1 is needed, and if not subset
       // invert the lhs now rather than inverting the result later
       if (decNumberIsNegative(rhs)) {   // was a **-n [hence digits>0]
-        decNumber *inv=invbuff;         // asssume use fixed buffer
+        decNumber *inv=invbuff;         // assume use fixed buffer
         decNumberCopy(&dnOne, dac);     // dnOne=1;  [needed now or later]
         #if DECSUBSET
         if (set->extended) {            // need to calculate 1/lhs
@@ -3798,7 +3798,7 @@ static void decToString(const decNumber *dn, char *string, Flag eng) {
 /*                                                                    */
 /* Addition, especially x=x+1, is speed-critical.                     */
 /* The static buffer is larger than might be expected to allow for    */
-/* calls from higher-level funtions (notable exp).                    */
+/* calls from higher-level functions (notable exp).                    */
 /* ------------------------------------------------------------------ */
 static decNumber * decAddOp(decNumber *res, const decNumber *lhs,
                             const decNumber *rhs, decContext *set,
@@ -4212,7 +4212,7 @@ static decNumber * decAddOp(decNumber *res, const decNumber *lhs,
 /* long subtractions.  These are acc and var1 respectively.           */
 /* var1 is a copy of the lhs coefficient, var2 is the rhs coefficient.*/
 /* The static buffers may be larger than might be expected to allow   */
-/* for calls from higher-level funtions (notable exp).                */
+/* for calls from higher-level functions (notable exp).                */
 /* ------------------------------------------------------------------ */
 static decNumber * decDivideOp(decNumber *res,
                                const decNumber *lhs, const decNumber *rhs,
@@ -5203,7 +5203,7 @@ static decNumber * decMultiplyOp(decNumber *res, const decNumber *lhs,
 /*    exp(-x) where x can be the tiniest number (Ntiny).              */
 /*                                                                    */
 /* 2. Normalizing x to be <=0.1 (instead of <=1) reduces loop         */
-/*    iterations by appoximately a third with additional (although    */
+/*    iterations by approximately a third with additional (although    */
 /*    diminishing) returns as the range is reduced to even smaller    */
 /*    fractions.  However, h (the power of 10 used to correct the     */
 /*    result at the end, see below) must be kept <=8 as otherwise     */

src/util.c

@@ -708,7 +708,7 @@ again:		switch (c = *fmt++) {
             continue;
 
         case 'x':	/* The date, using the locale's format. */
-            /* fall throug */
+            /* fall through */
 
         case 'D':	/* The date as "%y/%m/%d". */
         {