fcft: adapt to API changes in fcft-3.x

Fcft no longer uses wchar_t, but plain uint32_t to represent
codepoints.

Since we do a fair amount of string operations in foot, it still makes
sense to use something that actually _is_ a string (or character),
rather than an array of uint32_t.

For this reason, we switch out all wchar_t usage in foot to
char32_t. We also verify, at compile-time, that char32_t used
UTF-32 (which is what fcft expects).

Unfortunately, there are no string functions for char32_t. To avoid
having to re-implement all wcs*() functions, we add a small wrapper
layer of c32*() functions.

These wrapper functions take char32_t arguments, but then simply call
the corresponding wcs*() function.

For this to work, wcs*() must _also_ be UTF-32 compatible. We can
check for the presence of the  __STDC_ISO_10646__ macro. If set,
wchar_t is at least 4 bytes and its internal representation is UTF-32.

FreeBSD does *not* define this macro, because its internal wchar_t
representation depends on the current locale. It _does_ use UTF-32
_if_ the current locale is UTF-8.

Since foot enforces UTF-8, we simply need to check if __FreeBSD__ is
defined.

Other fcft API changes:

* fcft_glyph_rasterize() -> fcft_codepoint_rasterize()
* font.space_advance has been removed
* ‘tags’ have been removed from fcft_grapheme_rasterize()
* ‘fcft_log_init()’ removed
* ‘fcft_init()’ and ‘fcft_fini()’ must be explicitly called

.gitlab-ci.yml

@@ -17,6 +17,10 @@ debug-x64:
   image: alpine:edge
   stage: build
   script:
+    - cd subprojects
+    - git clone https://codeberg.org/dnkl/fcft.git
+    - cd fcft && git checkout 3.0-dev && cd ..
+    - cd ..
     - mkdir -p bld/debug
     - cd bld/debug
     - meson --buildtype=debug -Dgrapheme-clustering=enabled -Dfcft:grapheme-shaping=enabled -Dfcft:run-shaping=enabled -Dfcft:test-text-shaping=true ../../
@@ -31,6 +35,10 @@ debug-x64-no-grapheme-clustering:
   stage: build
   script:
     - apk del harfbuzz harfbuzz-dev utf8proc utf8proc-dev
+    - cd subprojects
+    - git clone https://codeberg.org/dnkl/fcft.git
+    - cd fcft && git checkout 3.0-dev && cd ..
+    - cd ..
     - mkdir -p bld/debug
     - cd bld/debug
     - meson --buildtype=debug -Dgrapheme-clustering=disabled -Dfcft:grapheme-shaping=disabled -Dfcft:run-shaping=disabled -Dfcft:test-text-shaping=false ../../
@@ -46,6 +54,10 @@ release-x64:
   image: alpine:edge
   stage: build
   script:
+    - cd subprojects
+    - git clone https://codeberg.org/dnkl/fcft.git
+    - cd fcft && git checkout 3.0-dev && cd ..
+    - cd ..
     - mkdir -p bld/release
     - cd bld/release
     - meson --buildtype=release -Dgrapheme-clustering=enabled -Dfcft:grapheme-shaping=enabled -Dfcft:run-shaping=enabled  -Dfcft:test-text-shaping=true ../../
@@ -61,6 +73,10 @@ debug-x86:
   image: i386/alpine:edge
   stage: build
   script:
+    - cd subprojects
+    - git clone https://codeberg.org/dnkl/fcft.git
+    - cd fcft && git checkout 3.0-dev && cd ..
+    - cd ..
     - mkdir -p bld/debug
     - cd bld/debug
     - meson --buildtype=debug -Dgrapheme-clustering=enabled -Dfcft:grapheme-shaping=enabled -Dfcft:run-shaping=enabled  -Dfcft:test-text-shaping=true ../../
@@ -76,6 +92,10 @@ release-x86:
   image: i386/alpine:edge
   stage: build
   script:
+    - cd subprojects
+    - git clone https://codeberg.org/dnkl/fcft.git
+    - cd fcft && git checkout 3.0-dev && cd ..
+    - cd ..
     - mkdir -p bld/release
     - cd bld/release
     - meson --buildtype=release -Dgrapheme-clustering=enabled -Dfcft:grapheme-shaping=enabled -Dfcft:run-shaping=enabled  -Dfcft:test-text-shaping=true ../../