Fix ${FILE_EXEC} and ${FILE_RUN}.  Also add their documents.
add feature silent compile when quickfix.  It won't enable in terminal.
add g:SingleCompile_showquickfixifwarning and its document
Merge branches 'silent' and 'warning'
Merge branch 'master' into v2.11-development
add g:SingleCompile_usetee
Merge branch 'master' into v2.11-development