Various fixes to avoid implicit function declarations.

Include <unistd.h> unconditionally because the configure script does
not define HAVE_UNISTD_H.  Add a few internal #include directives
that were missing.  Add the yylex, yyrestart, yyparse declarations
to ifm-main.h (instead of teaching flex & bison to generate a header
file; we do not even run bison during the build).

diff --git a/src/ifm-driver.c b/src/ifm-driver.c
index 5570297a96ad1d5e..850ac5de728f6ce4 100644
--- a/src/ifm-driver.c
+++ b/src/ifm-driver.c
@@ -33,6 +33,7 @@
 #include "ifm-raw.h"
 #include "ifm-rec.h"
 #include "ifm-dot.h"
+#include "ifm-main.h"
 
 /* Driver info */
 driver drivers[] = {
diff --git a/src/ifm-main.h b/src/ifm-main.h
index 9a03112d3f4060f2..cd4050c4e43dee67 100644
--- a/src/ifm-main.h
+++ b/src/ifm-main.h
@@ -21,6 +21,9 @@ extern vlist *ifm_styles;
 /* Advertised functions */
 extern int parse_input(char *file, int libflag, int required);
 extern void yyerror(char *msg);
+extern int yylex (void);
+extern void yyrestart (FILE *input_file);
+extern int yyparse (void);
 extern void err(char *fmt, ...);
 extern void warn(char *fmt, ...);
 extern void debug(char *fmt, ...);
diff --git a/src/ifm-parse.c b/src/ifm-parse.c
index 58b6ac0912d08a0e..5363f07c67de49a9 100644
--- a/src/ifm-parse.c
+++ b/src/ifm-parse.c
@@ -229,6 +229,7 @@
 #include "ifm-map.h"
 #include "ifm-util.h"
 #include "ifm-vars.h"
+#include "ifm-main.h"
 
 #define SET_LIST(object, attr, list) {                                  \
         vlist *l = vh_pget(object, attr);                               \
diff --git a/src/ifm-parse.y b/src/ifm-parse.y
index 1cd47ef7faa3cdcc..fbf82834ec848427 100644
--- a/src/ifm-parse.y
+++ b/src/ifm-parse.y
@@ -22,6 +22,7 @@
 #include "ifm-map.h"
 #include "ifm-util.h"
 #include "ifm-vars.h"
+#include "ifm-main.h"
 
 #define SET_LIST(object, attr, list) {                                  \
         vlist *l = vh_pget(object, attr);                               \
diff --git a/src/ifm-path.c b/src/ifm-path.c
index 71688727584d088a..e6ce4bba0b64e127 100644
--- a/src/ifm-path.c
+++ b/src/ifm-path.c
@@ -23,6 +23,7 @@
 #include "ifm-path.h"
 #include "ifm-task.h"
 #include "ifm-util.h"
+#include "ifm-vars.h"
 
 #define NODE(room)           vh_sgetref(room, "NODE")
 
diff --git a/src/libvars/vars-config.h b/src/libvars/vars-config.h
index da081a1da5920b85..b77fe7247848ee83 100644
--- a/src/libvars/vars-config.h
+++ b/src/libvars/vars-config.h
@@ -22,9 +22,7 @@
 #include <alloca.h>
 #endif
 
-#ifdef HAVE_UNISTD_H
 #include <unistd.h>
-#endif
 
 #ifdef HAVE_PROCESS_H
 #include <process.h>
diff --git a/src/libvars/vars-random.c b/src/libvars/vars-random.c
index 9393ff03faf8447f..fdac4ee1027d04dd 100644
--- a/src/libvars/vars-random.c
+++ b/src/libvars/vars-random.c
@@ -23,6 +23,7 @@
 
 #include "vars-config.h"
 #include "vars-random.h"
+#include "vars-utils.h"
 
 /* Required size of unsigned long */
 #define ULONG	4