Rename HB_VERSION_CHECK and hb_version_check to "atleast"

HB_VERSION_CHECK's comparison was originally written wrongly
by mistake.  When API tests were written, they were also written
wrongly to pass given the wrong implementation... Sigh.

Given the purpose of this API, there's no point in fixing it
without renaming it.  As such, rename.

API changes:

  HB_VERSION_CHECK -> HB_VERSION_ATLEAST
  hb_version_check -> hb_version_atleast

docs/reference/harfbuzz-sections.txt

diff --git a/docs/reference/harfbuzz-sections.txt b/docs/reference/harfbuzz-sections.txt
index 973009c..3612dad 100644
--- a/docs/reference/harfbuzz-sections.txt
+++ b/docs/reference/harfbuzz-sections.txt
@@ -487,12 +487,12 @@
 
 <SECTION>
 <FILE>hb-version</FILE>
-HB_VERSION_CHECK
+HB_VERSION_ATLEAST
 HB_VERSION_MAJOR
 HB_VERSION_MICRO
 HB_VERSION_MINOR
 HB_VERSION_STRING
 hb_version
-hb_version_check
+hb_version_atleast
 hb_version_string
 </SECTION>