Move C-related declarations to compile-c.h

This patch simply moves a bunch of C language-related declarations from
the various compile header files into a new C-specific header, compile-c.h.

gdb/ChangeLog:
        * Makefile.in (SUBDIR_GCC_COMPILE_SRCS): Move header files ...
        (HFILES_NO_SRCDIR): ... to here.
        Add compile-internal.h and compile-c.h.
        * compile/compile-c-support.c: Include compile-c.h.
        * compile/compile-c-symbols.c: Include compile-c.h.
        (generate_c_for_variable_locations): Update comment.
        * compile/compile-c-types.c: Include compile-c.h.
        * compile/compile-c.h: New file -- moved C language declarations
        from other files here.
        * compile/compile-internal.h: Do not include hashtab.h or
        common/enum-flags.h.
        (gcc_qualifiers_flags, struct compile_c_instance, C_CTX)
        (gcc_convert_symbol, gcc_symbol_address)
        (generate_c_for_variable_locations, c_get_mode_for_size)
        (c_get_range_decl_name): Definitions moved to compile-c.h.
        * compile/compile-loc2c.c: Include compile-c.h.

gdb/compile/compile-c.h

@@ -0,0 +1,81 @@
+/* Header file for GDB compile C-language support.
+   Copyright (C) 2014-2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDB_COMPILE_C_H
+#define GDB_COMPILE_C_H
+
+#include "common/enum-flags.h"
+#include "hashtab.h"
+
+/* enum-flags wrapper.  */
+
+DEF_ENUM_FLAGS_TYPE (enum gcc_qualifiers, gcc_qualifiers_flags);
+
+/* A callback suitable for use as the GCC C symbol oracle.  */
+
+extern gcc_c_oracle_function gcc_convert_symbol;
+
+/* A callback suitable for use as the GCC C address oracle.  */
+
+extern gcc_c_symbol_address_function gcc_symbol_address;
+
+/* A subclass of compile_instance that is specific to the C front
+   end.  */
+
+struct compile_c_instance
+{
+  /* Base class.  Note that the base class vtable actually points to a
+     gcc_c_fe_vtable.  */
+  struct compile_instance base;
+
+  /* Map from gdb types to gcc types.  */
+  htab_t type_map;
+
+  /* Map from gdb symbols to gcc error messages to emit.  */
+  htab_t symbol_err_map;
+};
+
+/* A helper macro that takes a compile_c_instance and returns its
+   corresponding gcc_c_context.  */
+
+#define C_CTX(I) ((struct gcc_c_context *) ((I)->base.fe))
+
+/* Emit code to compute the address for all the local variables in
+   scope at PC in BLOCK.  Returns a malloc'd vector, indexed by gdb
+   register number, where each element indicates if the corresponding
+   register is needed to compute a local variable.  */
+
+extern gdb::unique_xmalloc_ptr<unsigned char>
+  generate_c_for_variable_locations
+     (struct compile_c_instance *compiler,
+      string_file &stream,
+      struct gdbarch *gdbarch,
+      const struct block *block,
+      CORE_ADDR pc);
+
+/* Get the GCC mode attribute value for a given type size.  */
+
+extern const char *c_get_mode_for_size (int size);
+
+/* Given a dynamic property, return an xmallocd name that is used to
+   represent its size.  The result must be freed by the caller.  The
+   contents of the resulting string will be the same each time for
+   each call with the same argument.  */
+
+struct dynamic_prop;
+extern std::string c_get_range_decl_name (const struct dynamic_prop *prop);
+
+#endif /* GDB_COMPILE_C_H  */