tectonic/core-kpathutil.c: rename from tectonic/tidy_kpathutil.c

Continuing the project of making the names of the C/C++ source files more
sane. This file has code that has no specific dependence on the TeX engine or
external modules so we can classify it as "core".

Author: pkgw

build.rs

@@ -157,6 +157,7 @@ fn main() {
         .flag("-Wall")
         .file("tectonic/bibtex.c")
         .file("tectonic/core-bridge.c")
+        .file("tectonic/core-kpathutil.c")
         .file("tectonic/dpx-agl.c")
         .file("tectonic/dpx-bmpimage.c")
         .file("tectonic/dpx-cff.c")
@@ -239,7 +240,6 @@ fn main() {
         .file("tectonic/stringpool.c")
         .file("tectonic/synctex.c")
         .file("tectonic/texmfmp.c")
-        .file("tectonic/tidy_kpathutil.c")
         .file("tectonic/xetex0.c")
         .file("tectonic/XeTeX_ext.c")
         .file("tectonic/xetexini.c")

tectonic/tidy_kpathutil.c renamed to tectonic/core-kpathutil.c

@@ -146,7 +146,7 @@ extern scaled mult_and_add(integer n, scaled x, scaled y, scaled max_answer);
 extern scaled x_over_n(scaled x, integer n);
 extern scaled xn_over_d(scaled x, integer n, integer d);
 
-/* tidy_kpathutil.c */
+/* core-kpathutil.c */
 extern string xstrdup (const_string s);
 extern void *xmalloc (size_t size);
 extern void *xrealloc (void *old_address, size_t new_size);