Take into account 'gdefault' setting

If the user has 'gdefault' set (not the default), then the "g" flag
actually turns *off* global replacement instead of turning it on. So,
check for 'gdefault' in order to decide whether or not to pass the "g"
(we always want to do global replacements).

Reported here:

  https://twitter.com/briemens/status/1080554857998757888

My guess at problem here:

  https://twitter.com/wincent/status/1080616775681798144

Confirmed that it was here:

  https://twitter.com/briemens/status/1080618527218978816

autoload/scalpel.vim

@@ -30,6 +30,10 @@ function! scalpel#cword(curpos) abort
   return join(l:word, '')
 endfunction
 
+function s:g()
+  return &gdefault ? '' : 'g'
+endfunction
+
 function! scalpel#substitute(patterns, line1, line2, count) abort
   if a:count == -1
     " No range supplied, operate on whole buffer.
@@ -42,6 +46,8 @@ function! scalpel#substitute(patterns, line1, line2, count) abort
     let l:currentline=l:firstline
   endif
 
+  let l:g=s:g()
+
   " As per `:h E146`, can use any single-byte non-alphanumeric character as
   " delimiter except for backslash, quote, and vertical bar.
   if match(a:patterns, '\v^([^"\\|A-Za-z0-9 ]).*\1.*\1$') != 0
@@ -57,7 +63,7 @@ function! scalpel#substitute(patterns, line1, line2, count) abort
   let l:report=&report
   try
     set report=10000
-    execute l:currentline . ',' . l:lastline . 's' . a:patterns . 'gce#'
+    execute l:currentline . ',' . l:lastline . 's' . a:patterns . l:g . 'ce#'
   catch /^Vim:Interrupt$/
     execute 'set report=' . l:report
     return
@@ -80,7 +86,7 @@ function! scalpel#substitute(patterns, line1, line2, count) abort
       " Avoid unwanted "Backwards range given, OK to swap (y/n)?" messages.
       if l:currentline > l:firstline
         " Drop c flag.
-        execute l:firstline . ',' . l:currentline . '-&gce'
+        execute l:firstline . ',' . l:currentline . l:g . '-&ce'
       endif
      return
     endif
@@ -89,7 +95,7 @@ function! scalpel#substitute(patterns, line1, line2, count) abort
   " Loop around to top of range/file and continue.
   " Avoid unwanted "Backwards range given, OK to swap (y/n)?" messages.
   if l:currentline > l:firstline
-    execute l:firstline . ',' . l:currentline . '-&gce'
+    execute l:firstline . ',' . l:currentline . l:g . '-&ce'
     execute 'set report=' . l:report
   endif
 endfunction