enable a number of headers to be "compiled" standalone

I.e. to enable clangd-ing them. This is just adding some missing
includes that have been previously included in the whatever .h/.cc
files included those headers.

src/check_address-inl.h

diff --git a/src/check_address-inl.h b/src/check_address-inl.h
index 92c1740..f2b047b 100644
--- a/src/check_address-inl.h
+++ b/src/check_address-inl.h
@@ -32,9 +32,13 @@
 // stacktrace_generic_fp-inl.h module. We only split this into
 // separate header to enable unit test coverage.
 
+#include "config.h"
+
 // This is only used on OS-es with mmap support.
+#include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
+#include <stdint.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
@@ -42,6 +46,8 @@
 #include <sys/syscall.h>
 #endif
 
+#include "base/logging.h"
+
 namespace {
 
 #if defined(__linux__) && !defined(FORCE_PIPES)

src/getpc.h

diff --git a/src/getpc.h b/src/getpc.h
index c14c9d0..dcbbef4 100644
--- a/src/getpc.h
+++ b/src/getpc.h
@@ -49,6 +49,8 @@
 // REG_EIP).  Note this #define must come first!
 #define _GNU_SOURCE 1
 
+#include "config.h"
+
 #ifdef HAVE_ASM_PTRACE_H
 #include <asm/ptrace.h>
 #endif

src/heap-profile-stats.h

diff --git a/src/heap-profile-stats.h b/src/heap-profile-stats.h
index 1e075f7..d94afe8 100644
--- a/src/heap-profile-stats.h
+++ b/src/heap-profile-stats.h
@@ -51,6 +51,8 @@
 #ifndef HEAP_PROFILE_STATS_H_
 #define HEAP_PROFILE_STATS_H_
 
+#include <stdint.h>
+
 struct HeapProfileStats {
   // Returns true if the two HeapProfileStats are semantically equal.
   bool Equivalent(const HeapProfileStats& other) const {

src/libbacktrace_api.h

diff --git a/src/libbacktrace_api.h b/src/libbacktrace_api.h
index 2340a79..dde916f 100644
--- a/src/libbacktrace_api.h
+++ b/src/libbacktrace_api.h
@@ -32,6 +32,7 @@
 #define LIBBACKTRACE_API_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 extern "C" {
 

src/maybe_emergency_malloc.h

diff --git a/src/maybe_emergency_malloc.h b/src/maybe_emergency_malloc.h
index bbe20f6..48d891e 100644
--- a/src/maybe_emergency_malloc.h
+++ b/src/maybe_emergency_malloc.h
@@ -31,6 +31,8 @@
 #ifndef MAYBE_EMERGENCY_MALLOC_H
 #define MAYBE_EMERGENCY_MALLOC_H
 
+#include <stddef.h>
+
 #ifdef ENABLE_EMERGENCY_MALLOC
 
 #include "emergency_malloc.h"