Add support for COFF secidx relocations

bfd	* coff-i386.c (in_reloc_p): Add R_SECTION.
	(howto_table): Add R_SECTION.
	(coff_pe_i386_relocation_section): Add support for R_SECTION.
	(coff_i386_reloc_type_lookup): Add support for
	BFD_RELOC_16_SECCIDX.
	* coff-x86_64.c (in_reloc_p): Add R_SECTION.
	(howto_table): Add R_SECTION.
	(coff_pe_amd64_relocation_section): Add support for R_SECTION.
	(coff_amd64_reloc_type_lookup): Add support for
	BFD_RELOC_16_SECCIDX.
	* reloc.c: Add BFD_RELOC_16_SECIDX.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.

gas	* config/tc-i386.c (pe_directive_secidx): New function.
	(md_pseudo_table): Add support for secidx.
	(x86_cons_fix_new): Likewise.
	(tc_gen_reloc): Likewise.
	* expr.c (op_rank): Add O_secidx.
	* expr.h (operatorT): Likewise.
	* symbols.c (resolve_symbol_value): Add support for O_secidx.
	* testsuite/gas/i386/secidx.s: New test source file.
	* testsuite/gas/i386/secidx.d: New test driver file.
	* testsuite/gas/i386/i386.exp: Run new test.

include	* coff/i386.h: Define R_SECTION.
	* coff/x86_64.h: Likewise.

ld	* testsuite/ld-pe/secidx1.s: New test source file.
	* testsuite/ld-pe/secidx2.s: New test source file.
	* testsuite/ld-pe/secidx.d: New test driver file.
	* testsuite/ld-pe/secidx_64.d: New test driver file.
	* testsuite/ld-pe/pe.exp: Add new tests.

gas/expr.h

@@ -18,28 +18,27 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
-/*
- * By popular demand, we define a struct to represent an expression.
- * This will no doubt mutate as expressions become baroque.
- *
- * Currently, we support expressions like "foo OP bar + 42".  In other
- * words we permit a (possibly undefined) symbol, a (possibly
- * undefined) symbol and the operation used to combine the symbols,
- * and an (absolute) augend.  RMS says this is so we can have 1-pass
- * assembly for any compiler emissions, and a 'case' statement might
- * emit 'undefined1 - undefined2'.
- *
- * The type of an expression used to be stored as a segment.  That got
- * confusing because it overloaded the concept of a segment.  I added
- * an operator field, instead.
- */
+/* By popular demand, we define a struct to represent an expression.
+   This will no doubt mutate as expressions become baroque.
+
+   Currently, we support expressions like "foo OP bar + 42".  In other
+   words we permit a (possibly undefined) symbol, a (possibly
+   undefined) symbol and the operation used to combine the symbols,
+   and an (absolute) augend.  RMS says this is so we can have 1-pass
+   assembly for any compiler emissions, and a 'case' statement might
+   emit 'undefined1 - undefined2'.
+
+   The type of an expression used to be stored as a segment.  That got
+   confusing because it overloaded the concept of a segment.  I added
+   an operator field, instead.  */
 
 /* This is the type of an expression.  The operator types are also
    used while parsing an expression.
 
    NOTE: This enumeration must match the op_rank array in expr.c.  */
 
-typedef enum {
+typedef enum
+{
   /* An illegal expression.  */
   O_illegal,
   /* A nonexistent expression.  */
@@ -50,6 +49,8 @@ typedef enum {
   O_symbol,
   /* X_add_symbol + X_add_number - the base address of the image.  */
   O_symbol_rva,
+  /* The section index of X_add_symbol.  */
+  O_secidx,
   /* A register (X_add_number is register number).  */
   O_register,
   /* A big value.  If X_add_number is negative or 0, the value is in
@@ -112,7 +113,8 @@ typedef enum {
   O_max
 } operatorT;
 
-typedef struct expressionS {
+typedef struct expressionS
+{
   /* The main symbol.  */
   symbolS *X_add_symbol;
   /* The second symbol, if needed.  */
@@ -182,12 +184,10 @@ extern unsigned int get_single_number (void);
 extern symbolS *make_expr_symbol (expressionS * expressionP);
 extern int expr_symbol_where (symbolS *, const char **, unsigned int *);
 extern void current_location (expressionS *);
-
 extern symbolS *expr_build_uconstant (offsetT);
 extern symbolS *expr_build_dot (void);
 extern uint32_t generic_bignum_to_int32 (void);
 extern uint64_t generic_bignum_to_int64 (void);
-
-int resolve_expression (expressionS *);
+extern int resolve_expression (expressionS *);
 
 extern bool literal_prefix_dollar_hex;