config.nmake: Do some minor changes (mostly in comments).

- Update comment: /O2 enables /Gs which is "Control Stack Checking Calls" not "Buffer Security Check"
- Remove explicit setting of /GS (Buffer Security Check) since it's set by default.
  (The explicit setting did not apply to the CFLAGS used to compile Wireshark
   files because the setting was in the wrong place, but, fortunately, /GS is on
   by default.
- Add a comment about /GS being on by default.
- Remove some trailing whitespace.

Change-Id: I6cf631ee1ba0fb8556171861c7e5eb6d959c8f0c
Reviewed-on: https://code.wireshark.org/review/3228
Reviewed-by: Anders Broman <a.broman58@gmail.com>

config.nmake

@@ -968,6 +968,8 @@ APPVER=5.02
 #                                   This definition prevents the complaint about the redefinition of inline by WinPCap
 #                                   in pcap-stdinc.h when compiling CPP files, e.g. the QT UI
 #
+# -GS                               Stack-Based Buffer Overrun Detection: On by default for MSVC 2003 and later
+#                                    (See # http://msdn.microsoft.com/en-us/magazine/cc337897.aspx)
 # -O2                               http://msdn.microsoft.com/en-us/library/8f8h5cxt.aspx
 #                                   Specifying the /O2 compiler option is the same as using the following options:
 #                                   /Ob (Inline Function Expansion), where the option parameter is 2 (/Ob2)
@@ -975,7 +977,7 @@ APPVER=5.02
 #                                   /Oi (Generate Intrinsic Functions)
 #                                   /Ot (Favor Fast Code)
 #                                   /Oy (Frame-Pointer Omission)
-#                                   /Gs (Buffer Security Check)
+#                                   /Gs (Control Stack Checking Calls))
 #                                   /GF (Eliminate Duplicate Strings)
 #                                   /Gy (Enable Function-Level Linking)
 
@@ -1051,6 +1053,8 @@ LOCAL_CFLAGS= $(LOCAL_CFLAGS) /MP
 LOCAL_CFLAGS= $(LOCAL_CFLAGS) /analyze:WX-
 !ENDIF
 
+## Do *not* redefine LOCAL_CFLAGS below this point !!
+
 #STANDARD_CFLAGS are flags used for *Wireshark* compiles (not stuff like lemon, etc)
 STANDARD_CFLAGS=/DWINPCAP_VERSION=$(WINPCAP_VERSION) $(LOCAL_CFLAGS) $(WARNINGS_CFLAGS)
 
@@ -1077,7 +1081,6 @@ DLL_LDFLAGS = /MANIFEST:no
 # Enable Safe Exception Handler.
 # http://msdn.microsoft.com/en-us/magazine/cc337897.aspx
 !IF $(MSC_VER_REQUIRED) >= 1300
-LOCAL_CFLAGS= $(LOCAL_CFLAGS) /GS
 !IF "$(WIRESHARK_TARGET_PLATFORM)" != "win64"
 LOCAL_LDFLAGS= $(LOCAL_LDFLAGS) /SafeSEH
 !ENDIF
@@ -1111,7 +1114,7 @@ ENABLE_LIBWIRESHARK=USE
 #
 # install (debug) directory for Wireshark (relative to your source dir)
 INSTALL_DIR=wireshark-gtk2
-INSTALL_DIR_QT=wireshark-qt-release 
+INSTALL_DIR_QT=wireshark-qt-release
 
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