[gfortran,committed] Fix doc of -fsyntax-only

[FX Coudert]

Committed as rev. 127228 after checking with make info && make html.  
This adds a tiny little more detail to the documentation of -fsyntax- 
only.


Index: invoke.texi
===================================================================
--- invoke.texi (revision 127224)
+++ invoke.texi (working copy)
@@ -360,7 +360,9 @@ messages produced.
@item -fsyntax-only
@opindex @code{fsyntax-only}
@cindex syntax checking
-Check the code for syntax errors, but don't do anything beyond that.
+Check the code for syntax errors, but don't actually compile it.  This
+will generate module files for each module present in the code, but no
+other output file.
@item -pedantic
@opindex @code{pedantic}