[gdb/testsuite] Fix missing uint8_t in gdb.fortran/logical.exp

With test-case gdb.fortran/logical.exp, I run into:
...
(gdb) PASS: gdb.fortran/logical.exp: var=l: get hexadecimal valueof "&l"
set *((uint8_t *) 0x7fffffffd2bc) = 0xff^M
No symbol "uint8_t" in current context.^M
(gdb) FAIL: gdb.fortran/logical.exp: var=l: byte 0: set contents of byte at offset 0
...

Fix this by using the fortran-native type character instead.

Tested on x86_64-linux, with gcc 7.5.0 and clang 5.0.2.

gdb/testsuite/ChangeLog:

2020-03-04  Tom de Vries  <tdevries@suse.de>

	* gdb.fortran/logical.f90: Define variable with character type.
	* gdb.fortran/logical.exp: Use character type instead of uint8_t.

---
 gdb/testsuite/gdb.fortran/logical.exp | 2 +-
 gdb/testsuite/gdb.fortran/logical.f90 | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.fortran/logical.exp b/gdb/testsuite/gdb.fortran/logical.exp
index 96e6f8f955..324714fa49 100644
--- a/gdb/testsuite/gdb.fortran/logical.exp
+++ b/gdb/testsuite/gdb.fortran/logical.exp
@@ -43,7 +43,7 @@ foreach_with_prefix var { l l1 l2 l4 l8 } {
 
     for { set i 0 } { $i < $len } { incr i } {
 	with_test_prefix "byte $i" {
-	    gdb_test_no_output "set *((uint8_t *) ${addr}) = 0xff" \
+	    gdb_test_no_output "set *((character *) ${addr}) = 0xff" \
 		"set contents of byte at offset $i"
 	    gdb_test "p l" " = \\.TRUE\\."
 	    incr addr
diff --git a/gdb/testsuite/gdb.fortran/logical.f90 b/gdb/testsuite/gdb.fortran/logical.f90
index aea78e7089..175dfd1fc5 100644
--- a/gdb/testsuite/gdb.fortran/logical.f90
+++ b/gdb/testsuite/gdb.fortran/logical.f90
@@ -21,10 +21,12 @@ program test
   logical (kind=2) :: l2
   logical (kind=4) :: l4
   logical (kind=8) :: l8
+  character :: c
   l = .TRUE.
   l1 = .TRUE.
   l2 = .TRUE.
   l4 = .TRUE.
   l8 = .TRUE.
   l = .FALSE.					! stop-here
+  c = 'a'
 end