Fix spelling errors in the doc

[YangZhihui]

Summary

Fix some spelling error in the doc

clang/docs/ClangCommandLineReference.rst

 Only run preprocess and compilation steps
 
 .. option:: -c, --compile
 
 Only run preprocess, compile, and assemble steps
 
 .. option:: -emit-interface-stubs
 
-Generate Inteface Stub Files.
+Generate Interface Stub Files.
 
 .. option:: -emit-llvm
 
 Use the LLVM representation for assembler and object files
 
 .. option:: -emit-merged-ifs
 
 Generate Interface Stub Files, emit merged text not binary.

 .. option:: -fsplit-stack
 
 .. option:: -fstack-clash-protection
 
 Enable stack clash protection
 
 .. option:: -fstack-protector, -fno-stack-protector
 
-Enable stack protectors for some functions vulnerable to stack smashing. This uses a loose heuristic which considers functions vulnerable if they contain a char (or 8bit integer) array or constant sized calls to alloca , which are of greater size than ssp-buffer-size (default: 8 bytes). All variable sized calls to alloca are considered vulnerable. A function witha stack protector has a guard value added to the stack frame that is checked on function exit. The guard value must be positioned in the stack frame such that a buffer overflow from a vulnerable variable will overwrite the guard value before overwriting the function's return address. The reference stack guard value is stored in a global variable.
+Enable stack protectors for some functions vulnerable to stack smashing. This uses a loose heuristic which considers functions vulnerable if they contain a char (or 8bit integer) array or constant sized calls to alloca , which are of greater size than ssp-buffer-size (default: 8 bytes). All variable sized calls to alloca are considered vulnerable. A function with a stack protector has a guard value added to the stack frame that is checked on function exit. The guard value must be positioned in the stack frame such that a buffer overflow from a vulnerable variable will overwrite the guard value before overwriting the function's return address. The reference stack guard value is stored in a global variable.
 
 .. option:: -fstack-protector-all
 
 Enable stack protectors for all functions
 
 .. option:: -fstack-protector-strong
 
 Enable stack protectors for some functions vulnerable to stack smashing. Compared to -fstack-protector, this uses a stronger heuristic that includes functions containing arrays of any size (and any type), as well as any calls to alloca or the taking of an address from a local variable