Clean up #includes

Remove unused headers, and avoid relying on transitive inclusions

`include-what-you-use` has been very useful for this!

src/asm/charmap.cpp

@@ -2,7 +2,6 @@
 
 #include "asm/charmap.hpp"
 
-#include <errno.h>
 #include <stack>
 #include <stdio.h>
 #include <stdlib.h>
@@ -11,8 +10,6 @@
 
 #include "util.hpp"
 
-#include "asm/main.hpp"
-#include "asm/output.hpp"
 #include "asm/warning.hpp"
 
 // Charmaps are stored using a structure known as "trie".

src/asm/fixpoint.cpp

@@ -6,9 +6,6 @@
 
 #include <math.h>
 
-#include "asm/symbol.hpp"
-#include "asm/warning.hpp"
-
 #ifndef M_PI
 	#define M_PI 3.14159265358979323846
 #endif

src/asm/fstack.cpp

@@ -10,7 +10,6 @@
 #include <stack>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string_view>
 
 #include "error.hpp"
 #include "helpers.hpp"

src/asm/lexer.cpp

@@ -12,7 +12,6 @@
 #include <inttypes.h>
 #include <limits.h>
 #include <math.h>
-#include <new>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

src/asm/parser.y

@@ -45,7 +45,6 @@
 %code {
 	#include <algorithm>
 	#include <ctype.h>
-	#include <errno.h>
 	#include <inttypes.h>
 	#include <stdio.h>
 	#include <stdlib.h>

src/asm/rpn.cpp

@@ -3,7 +3,6 @@
 #include "asm/rpn.hpp"
 
 #include <assert.h>
-#include <errno.h>
 #include <inttypes.h>
 #include <limits.h>
 #include <stdio.h>
@@ -13,7 +12,6 @@
 
 #include "opmath.hpp"
 
-#include "asm/main.hpp"
 #include "asm/output.hpp"
 #include "asm/section.hpp"
 #include "asm/symbol.hpp"

src/asm/section.cpp

@@ -12,6 +12,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "helpers.hpp"
+
 #include "asm/fstack.hpp"
 #include "asm/lexer.hpp"
 #include "asm/main.hpp"

src/asm/symbol.cpp

@@ -3,13 +3,11 @@
 #include "asm/symbol.hpp"
 
 #include <assert.h>
-#include <errno.h>
 #include <inttypes.h>
 #include <stdio.h>
 #include <unordered_map>
 
 #include "error.hpp"
-#include "helpers.hpp"
 #include "version.hpp"
 
 #include "asm/fstack.hpp"