PR fortran/95827 - Buffer overflows with submodules and coarrays

With submodules and coarrays, name mangling results in long internal
symbols.  Enlarge internal buffer.

gcc/fortran/
	PR fortran/95827
	* iresolve.c (gfc_get_string): Enlarge internal buffer used in
	generating the mangled name.

(cherry picked from commit a16d0924f18046704ef9a4b6d9593718594677f1)

gcc/fortran/iresolve.c

@@ -47,8 +47,8 @@ along with GCC; see the file COPYING3.  If not see
 const char *
 gfc_get_string (const char *format, ...)
 {
-  /* Provide sufficient space to hold "_F.symbol.symbol_MOD_symbol".  */
-  char temp_name[4 + 2*GFC_MAX_SYMBOL_LEN + 5 + GFC_MAX_SYMBOL_LEN + 1];
+  /* Provide sufficient space for "_F.caf_token__symbol.symbol_MOD_symbol".  */
+  char temp_name[15 + 2*GFC_MAX_SYMBOL_LEN + 5 + GFC_MAX_SYMBOL_LEN + 1];
   const char *str;
   va_list ap;
   tree ident;

gcc/testsuite/gfortran.dg/pr95827.f90

+! { dg-do compile }
+! { dg-options "-fcoarray=lib -fsecond-underscore" }
+! PR fortran/95827 - ICE in gfc_get_string, at fortran/iresolve.c:70
+
+module m2345678901234567890123456789012345678901234567890123456789_123
+  interface
+     module subroutine s2345678901234567890123456789012345678901234567890123456789_123
+     end
+   end interface
+end
+submodule(m2345678901234567890123456789012345678901234567890123456789_123) &
+          n2345678901234567890123456789012345678901234567890123456789_123
+  integer :: x2345678901234567890123456789012345678901234567890123456789_123[*]
+end