libsysdecode: grab shmflags from sys/mman.h, add decode method

Any SHM_* flag here is (and likely will continue to be) a shmflag that may
be passed to shm_open2(), with exception to SHM_ANON. This is a prereq to
adding appropriate support to truss/kdump.

Reviewed by:	kaktus (slightly earlier version)
Differential Revision:	https://reviews.freebsd.org/D23733

lib/libsysdecode/flags.c

@@ -1277,3 +1277,10 @@ sysdecode_sctp_sinfo_flags(FILE *fp, int sinfo_flags)
 		}
 	}
 }
+
+bool
+sysdecode_shmflags(FILE *fp, int flags, int *rem)
+{
+
+	return (print_mask_0(fp, shmflags, flags, rem));
+}

lib/libsysdecode/mktables

@@ -165,6 +165,7 @@ if [ -e "${include_dir}/x86/sysarch.h" ]; then
 else
 	gen_table "sysarchnum" "[A-Z_]+[[:space:]]+[0-9]+"                 "machine/sysarch.h"
 fi
+gen_table "shmflags"  "SHM_[A-Z_]+[[:space:]]+0x[0-9]+"                    "sys/mman.h"         "SHM_ANON"
 
 # Generate a .depend file for our output file
 if [ -n "$output_file" ]; then

lib/libsysdecode/sysdecode.h

@@ -128,5 +128,6 @@ const char *sysdecode_vmresult(int _result);
 bool	sysdecode_wait4_options(FILE *_fp, int _options, int *_rem);
 bool	sysdecode_wait6_options(FILE *_fp, int _options, int *_rem);
 const char *sysdecode_whence(int _whence);
+bool	sysdecode_shmflags(FILE *_fp, int _flags, int *_rem);
 
 #endif /* !__SYSDECODE_H__ */