[gdb] Fix common misspellings

Fix the following common misspellings:
...
accidently -> accidentally
additonal -> additional
addresing -> addressing
adress -> address
agaisnt -> against
albiet -> albeit
arbitary -> arbitrary
artifical -> artificial
auxillary -> auxiliary
auxilliary -> auxiliary
bcak -> back
begining -> beginning
cannonical -> canonical
compatiblity -> compatibility
completetion -> completion
diferent -> different
emited -> emitted
emiting -> emitting
emmitted -> emitted
everytime -> every time
excercise -> exercise
existance -> existence
fucntion -> function
funtion -> function
guarentee -> guarantee
htis -> this
immediatly -> immediately
layed -> laid
noone -> no one
occurances -> occurrences
occured -> occurred
originaly -> originally
preceeded -> preceded
preceeds -> precedes
propogate -> propagate
publically -> publicly
refering -> referring
substract -> subtract
substracting -> subtracting
substraction -> subtraction
taht -> that
targetting -> targeting
teh -> the
thier -> their
thru -> through
transfered -> transferred
transfering -> transferring
upto -> up to
vincinity -> vicinity
whcih -> which
whereever -> wherever
wierd -> weird
withing -> within
writen -> written
wtih -> with
doesnt -> doesn't
...

Tested on x86_64-linux.

gdb/dwarf2/frame.c

@@ -911,7 +911,7 @@ dwarf2_frame_cache (const frame_info_ptr &this_frame, void **this_cache)
      its return address.  As a result the return address will
      point at some random instruction, and the CFI for that
      instruction is probably worthless to us.  GCC's unwinder solves
-     this problem by substracting 1 from the return address to get an
+     this problem by subtracting 1 from the return address to get an
      address in the middle of a presumed call instruction (or the
      instruction in the associated delay slot).  This should only be
      done for "normal" frames and not for resume-type frames (signal
@@ -1073,7 +1073,7 @@ incomplete CFI data; unspecified registers (e.g., %s) at %s"),
 	    ULONGEST retaddr_column = fs.retaddr_column;
 
 	    /* It seems rather bizarre to specify an "empty" column as
-	       the return adress column.  However, this is exactly
+	       the return address column.  However, this is exactly
 	       what GCC does on some targets.  It turns out that GCC
 	       assumes that the return address can be found in the
 	       register corresponding to the return address column.