avoid top margin on input-append/prepend in .navbar-form

docs/assets/css/bootstrap.css

@@ -4197,6 +4197,8 @@ input[type="submit"].btn.btn-mini {
   white-space: nowrap;
 }
 
+.navbar-form .input-append .btn,
+.navbar-form .input-prepend .btn,
 .navbar-form .input-append input,
 .navbar-form .input-prepend input {
   margin-top: 0;

less/navbar.less

@@ -90,10 +90,11 @@
   .navbarVerticalAlign(28px); // Vertically center in navbar
 }
 .navbar .btn-group .btn {
-  margin: 0; // then undo the margin here so we don't accidentally double it
+  margin-top: 0; // then undo the margin here so we don't accidentally double it
 }
 
 // Navbar forms
+// -------------------------
 .navbar-form {
   margin-bottom: 0; // remove default bottom margin
   .clearfix();
@@ -125,6 +126,7 @@
 }
 
 // Navbar search
+// -------------------------
 .navbar-search {
   position: relative;
   float: left;