many Standard C declarations are @safe

src/core/stdc/complex.d

@@ -15,7 +15,7 @@
 module core.stdc.complex;
 
 extern (C):
-@trusted: // All of these operate on floating point values only.
+@safe: // All of these operate on floating point values only.
 nothrow:
 @nogc:
 

src/core/stdc/ctype.d

@@ -15,7 +15,7 @@
 module core.stdc.ctype;
 
 extern (C):
-@trusted: // All of these operate on integers only.
+@safe: // All of these operate on integers only.
 nothrow:
 @nogc:
 

src/core/stdc/errno.d

@@ -39,7 +39,7 @@ version (SystemZ) version = IBMZ_Any;
 version (X86)     version = X86_Any;
 version (X86_64)  version = X86_Any;
 
-@trusted: // Only manipulates errno.
+@safe: // Only manipulates errno.
 nothrow:
 @nogc:
 

src/core/stdc/float_.d

@@ -15,7 +15,7 @@
 module core.stdc.float_;
 
 extern (C):
-@trusted: // Constants only.
+@safe: // Constants only.
 nothrow:
 @nogc:
 

src/core/stdc/inttypes.d

@@ -18,7 +18,7 @@ public import core.stdc.stddef; // for wchar_t
 public import core.stdc.stdint; // required by spec
 
 extern (C):
-@trusted: // Types and constants only.
+@safe:
 nothrow:
 @nogc:
 
@@ -430,14 +430,14 @@ else
 }
 
 ///
-intmax_t  imaxabs(intmax_t j);
+@safe intmax_t  imaxabs(intmax_t j);
 ///
-imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
+@safe imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
 ///
-intmax_t  strtoimax(const scope char* nptr, char** endptr, int base);
+@system intmax_t  strtoimax(const scope char* nptr, char** endptr, int base);
 ///
-uintmax_t strtoumax(const scope char* nptr, char** endptr, int base);
+@system uintmax_t strtoumax(const scope char* nptr, char** endptr, int base);
 ///
-intmax_t  wcstoimax(const scope wchar_t* nptr, wchar_t** endptr, int base);
+@system intmax_t  wcstoimax(const scope wchar_t* nptr, wchar_t** endptr, int base);
 ///
-uintmax_t wcstoumax(const scope wchar_t* nptr, wchar_t** endptr, int base);
+@system uintmax_t wcstoumax(const scope wchar_t* nptr, wchar_t** endptr, int base);

src/core/stdc/limits.d

@@ -26,7 +26,7 @@ else version (WatchOS)
 private import core.stdc.config;
 
 extern (C):
-@trusted: // Constants only.
+@safe: // Constants only.
 nothrow:
 @nogc:
 

src/core/stdc/locale.d

@@ -24,7 +24,7 @@ else version (WatchOS)
     version = Darwin;
 
 extern (C):
-@trusted: // Only setlocale operates on C strings.
+@safe: // Only setlocale operates on C strings.
 nothrow:
 @nogc:
 
@@ -289,4 +289,4 @@ else
 ///
 @system char*  setlocale(int category, const scope char* locale);
 ///
-lconv* localeconv();
+@safe lconv* localeconv();

src/core/stdc/stddef.d

@@ -15,7 +15,7 @@
 module core.stdc.stddef;
 
 extern (C):
-@trusted: // Types only.
+@safe: // Types only.
 nothrow:
 @nogc:
 

src/core/stdc/stdint.d

@@ -28,11 +28,11 @@ else version (TVOS)
 else version (WatchOS)
     version = Darwin;
 
-// Can't be `private` because of @@@BUG11173@@@.
+// Can't be `private` because of http://issues.dlang.org/show_bug.cgi?id=11173
 T _typify(T)(T val) @safe pure nothrow { return val; }
 
 extern (C):
-@trusted: // Types and constants only.
+@safe: // Types and constants only.
 nothrow:
 @nogc:
 

src/core/stdc/tgmath.d

@@ -19,7 +19,7 @@ private static import core.stdc.math;
 private static import core.stdc.complex;
 
 extern (C):
-@trusted: // Everything here operates on floating point and integer values.
+@safe: // Everything here operates on floating point and integer values.
 nothrow:
 @nogc:
 

src/core/stdc/wctype.d

@@ -17,7 +17,7 @@ module core.stdc.wctype;
 public  import core.stdc.wchar_; // for wint_t, WEOF
 
 extern (C):
-@trusted: // Only a couple of functions below operate on unsafe C strings.
+@safe: // Only a couple of functions below operate on unsafe C strings.
 nothrow:
 @nogc: