Added required Pop's to nsExec example usage

git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@6967 212acab6-be3b-0410-9dea-997c60f758d6

Contrib/nsExec/nsExec.txt

@@ -7,14 +7,18 @@ without opening a dos box.
 Usage
 -----
 nsExec::Exec [/OEM] [/TIMEOUT=x] path
+Pop $0
 
 -or-
 
 nsExec::ExecToLog [/OEM] [/TIMEOUT=x] path
+Pop $0
 
 -or-
 
 nsExec::ExecToStack [/OEM] [/TIMEOUT=x] path
+Pop $0 ; Return
+Pop $1 ; Output
 
 All functions are the same except ExecToLog will print the output
 to the log window and ExecToStack will push up to ${NSIS_MAX_STRLEN}